The Humble Every Day Carry
When I first went back to a pen and paper I discovered I never wanted to be without. Rain, snow or shine: pens, pencils and paper will be there for you. Day of night, power, no power too. These simple tools will 'just work'. I've had phones and digital organizers fail because of drained batteries, getting wet and getting too warm or cold. Analog beats digital for an every day carry every time.
Like everything analog, there are loads of options for every day carry needs. I usually tell people to find a pocket sized option for paper and a pen or pencil they are willing to lose or have stolen. I also tell people to ensure their setup is waterproof.
Loss / Theft
I tell others to pick items that can be lost or stolen mainly because both happen. I know I'd be very upset someone stole a writing instrument that took six months of savings to buy. I'd be mad if it fell out of my pocket and was lost forever too. It may seem silly but I implore you to consider both theft and loss when choosing your every day carry supplies. Everything I mention here I'd consider loss/theft compatible.
Rain, Snow and Shine
Rain, snow and shine are the other big things I tell people to consider when selecting an every day carry setup. I've needed to jot something down indoors, outdoors on sunny days, in rain storms and in blizzards. Because of this, my daily carry is durable and waterproof. I like the ability to write without worry. However, I can be considered 'hardcore' at times. If nothing else consider this: spilling your drink across the page. It happens. Maybe you only need to worry about a spill. If that's the case, keep water proofing in mind if/when selecting a pen. Pencil should always be waterproof, I've yet to see a pencil that's not waterproof.
Before I go too much further I would like to define what I consider an every day carry. I see an every day carry as paper and writing instrument that fits comfortably in my pocket. For me that means an A6 sized notebook (4" x 6" for those in the USA) and a pen or pencil that's about as tall as the notebook. My comments on options are framed with this in mind. It's what works for me and others. That said: every day carry is what you carry around. If you prefer something larger or smaller, don't let my words drive you away from something you feel works better for you. The every day carry is rooted in personal preference. We are all simultaneously right and wrong. Find your version of pocket sized and go from there. Or just use A6 or 4"x6" as a starting point. The paper options I give below are available in more than one size and style.
For an every day carry I tend to recommend a pen or pencil. This may seem terribly open ended. It is. What an individual uses to write is so intensely personal I don't think I could pen words to do it justice.
As an every day carry I like to suggest you use a good pencil or a 'common' style pen. Most people have used pencils, ballpoint pens and rollerball pens. People also tend to borrow pens if they are in need and see yours. I know I wouldn't want to hand off an extra fine fountain pen to anyone that doesn't have experience with a fountain pen. That's a recipe for a ruined nib.
There are a large number of pencils, ballpoint pens and rollerball pens out there. I'd strongly recommend finding one you like but would still be willing to hand out in a pinch. It may take a few false starts but you should be able to find one pretty quickly.
If you opt for a pencil for your every day carry I'd recommend a 0.7mm mechanical pencil or 2mm lead holder. 0.7mm and 2mm leads are common, less fragile than 0.5mm and last a long time. There are also many makers of 0.7mm and 2mm lead out there and many hardness levels. Lots and lots of options for finding what works best for you. I'm personally partial to 2mm leads (and holders) as they act like a traditional wood pencil without the need for a sharpener. You can find 2mm lead holders that are good quality for cheap (Staedtler for example) or 'high end' (rOtring for example). Mine preference is a Staedtler 2mm lead holder with HB Staedtler leads.
Before I move on I should note: pencils are almost always waterproof. I have yet to use a pencil or lead that won't write when wet or survive being soaked. However, I have had fading problems 'over time' with pencil. I don't think fading will be an issue for most every day carries but I think it deserves mention since I've seen it before.
Ah... the 'adult' version of a writing instrument. What we desire as children and come to lean on as adults. As an every day carry you can't go wrong with a pen. Notes, signing things, loaning to another human. Great utility to be had with a pen. I'd recommend a ballpoint or rollerball for an every day carry. It will let you lend it to someone else without worry. A fountain pen can't be lent freely (in my humble opinion) and people don't appreciate it if you withhold a pen (trust me). If you'd like a nicer pen than the bargain bin offers, there are an absurd number of ballpoint and rollerball pens that use refills. There are a great many refills to choose from as well. I went this route for my every day carry: a pen that is nearly universal in its refill support and my favorite refill. Finding a pen/refill can be a pain (I tried a dozen or so) but once you find 'the right one' all you need to do is stock up.
Now that I've covered pens: a quick note on inks. Inks vary wildly in their properties. I look for inks that are waterproof and fast drying. However, these may not be needs of yours. If nothing else, run a test to see. Write a sentence on a page and run it under the faucet while rubbing the text lightly with your finger. If nothing else: you'll know how long you have to cleanup a spill or if your writing will survive a good soaking.
If waterproofing is something you want, the Fisher Space Pen refills are waterproof, the Ohto refills are waterproof and the Pilot G2 refills are not waterproof or spill resistant. In general the ballpoint refills tend to be more water resistant (even if not advertised as such) and the rollerball refills less water resistant. There are exceptions (the Ohto for example) and the best way to find out is to give a refill a try if it's not advertised. I use the Ohto 0.4mm refills in blak due to the quality of the rollerball (it's similar to a fountain pen) and the ink being waterproof once dry.
Notebooks / Paper
Now that the instruments are out of the way it's time for... PAPER!. Put simply: don't let the 'cool kids' fool you. Any paper is good if it means you're happy. Almost any paper you'll find will survive a spill, be reasonably water proof and work well enough with your chosen writing instrument.
That said: there are two cheap, nicely textured (read: smooth), well tempermented paper options you'll see regularly used for every day carries. FieldNotes and Rhodia. Both are available in pocket sizes and Rhodia has a wide range of options to choose from if you want bigger/smaller than A6. If you're not sure, start with FieldNotes (cheaper) and then move into Rhodia. Start with Rhodia if you want something larger or smaller than A6 sized pages. I personally prefer FieldNotes but have used the Rhodia (and other) offerings with success.
If you want to go 'all in' on waterproof and heavy duty you'll want to look into Rite in the Rain notebooks and the FieldNotes Expedition series. Both are very rugged and 100% waterproof. To the point you won't know the pages got wet and they are meant to be used in the rain. The Rite in the Rain pages are wax coated paper and only work with pencil or ballpoint pens. The FieldNotes Expedition pages are plastic (yes, plastic) and only work with pencil and very specific ballpoint pens. Both Rite in the Rain and FieldNotes have published info on what writing instruments work well with these notebooks. You'll want to take note if purchasing either. I personally prefer Rite in the Rain but have used the FieldNotes Expedition. If I use either, I use a Fisher Space Pen refill or 2mm lead holders with them. If you want waterproof and/or indestructible, these are your notebooks.
OK, that was a ton of info, I'll admit that. Distilled: it's basically a bunch of options and ideas for an every day carry writing setup.
I use a Karas Kustoms Retrakt with 0.4mm Ohto black refill and FieldNotes Pitch Black notebooks in a waxed canvas cover. I outlined this post using them. I've also used a tactical pen with Fisher Space pen black refills and 4"x6" Rite in the Rain notebook when spending time outdoors in the woods. I know my preferences are likely different than most (FieldNotes aside) and I didn't hit on the combo right away. I tried more than a few options (paper, pencil, pen) and dialed in my preferences over time.
This post is all about providing a starting point for finding your preferred every day carry and so you know there are options. The products and options I've detailed here are a starting point for ideas and branching out.
If you already prefer a pen or paper or pencil, start there and build your every day carry from that starting point.
Just don't give up, your every day carry is out there, it just may be slightly out of sight.