i personally skin for jcink but i've skinned for proboards and to a certain extent, it's not too terribly different that far into the back end (i just don't remember a lot of it), jcink is just. a ton easier since jcink has a wikia that flat out lays out every single possible variable you can use (with maybe 2 exceptions that i've found), so it's a lot easier to work with than "do i know what this does exactly? no. do i hope i have the general idea right? yes."

i personally start by working on a codepen page since jcink is super easy to just pick up the raw html and plop it down in with maybe a day of converting (compared to two or three coding each part in codepen if i'm designing from scratch). i like starting with the header area and then working down through the boards and the info center, then maybe doing threads, then doing either profile and post + mini-profile. from there i'll move it over and start working on the site itself for anything extra usually. or in other words, i code as much as i can raw-skin-wise on the codepen and then move it over since codepen is nice for auto refresh in one window where jcink you gotta jump between 5 tabs.

is it the greatest system? no. does it always work on proboards? again, no. but it at least means that i know how it all fits together and have a separate place with the coding in case i need to hard bomb the skin and start over. which is always useful tbeh, so. yeah.

i also personally have to start with colors first since i'm terrible with design otherwise, so if i don't know what i'm working with to start, ho boy, things are gonna go poorly by the time we start trying to make the skin not-monochrome. variables are my friends and i love them so very much and i don't know what i'd do without them now that i know how they work tbeh, i love being able to change 1 line in the code and fix the colors everywhere omg

This is definitely personal preference, rather than cut and dry advice that I recommend anyone and everyone do – Kitten's comment on focusing on front page and posting above all is definitely spot-on in terms of genuine advice – but seeing how a frequent coder tackles things step-by-step can maybe help you to decide how to tackle things on your own?

I always begin a skin with an idea – never with the entire design of the forum in mind, and sometimes an idea that's just as vague as a shape I'd like to be prominent across the design, but always with some baseline I can go back to. Usually, this includes, at the very least, a rough layout of the banner area, if not a very-close-to-final draft of what said banner will look like in my head. I always begin with the banner, since this is what people's very first impression will be. It's also, like, the highest density place for information regarding your site, containing things like blurbs, quick links, and the like, and these things can fluctuate depending on what sort of site it is, or even how much space you allot yourself. If I've decided beforehand to do a sidebar, that's coded immediately after the banner area, fixed or scrolling, since sidebars, functionally, are just a taller version of the banner, skjdfhlkdsjfhds.

From there, I work down the front page; the board remodel always follows immediately after banner (or sidebar), and with that done, I usually beeline for the info center to get the homepage done first and foremost. If I'm particularly struggling with info center designs and already have some idea of what I'd like to do for a mini-profile, I may skip it in favor of the latter, but the info center comes immediately after the mini-profile in the case of a change. The bottom of the forum – like affiliates, credits if they're not listed in the banner, and so on – is usually lumped in with the info center, despite being coded in two different Layout Templates. Thread list comes after, usually because I'm burnt out by this point if I'm cram coding (which I usually am, oops) and thread lists are stupid simple to design, and the final and most difficult remodel, the user-profile, comes last. From there, slight touch-ups and cleanups can be made along the way.

The banner, aesthetically, is important, because you can draw most of your design elements from it for every other aspect of your site. If you've coded, say, arrows into your banner, using arrows in your board list, mini-profile, and so on can help your design overall look more cohesive. As a person design rule, I try not to do anymore than three of one “type” - no more than three custom fonts, no more than three accent colors (unless it's rainbow, that doesn't count, sdkljfhdjkhds), no more than three styles of hover effects, no more than three shapes (although USUALLY, I try to stick with two – diamonds and circles, arrows and squares, whatever). The more “things” you try to add to your design, the less room there is for repetition, and the less... well, cohesive that design will end up looking in the end!

Accent colors should be able to be changed on the fly. I've done skins where halfway through, I decided I wanted it to be blue instead of green (usually 'cause I found a cooler banner image) and just overhauled all the accents. Colors chosen for background colors and text are a little trickier. You'll probably want to know going in if you're doing a light or a dark skin. If you intend to change it at any point in the future, keep that in mind while coding it the first time around.