This is a crucial step. It will save you time, confusion, etc. There is a lot that goes into doing a Webcomic so being prepared is the smart way to go. I’ll try to cover as many steps as I can remember that will help you. All this might seem daunting, but trust me when I say this will save you time.
You should have a form of documentation that tells all your characters, places, descriptions, and anything you feel will need to be on hand when diving into your Webcomic. This should also be in an easy to reach place. I have a character in my Webcomic with the strangest name spelling. It saves me time in trying to remember and/or hunt the proper way to spell it. You can avoid mistakes as well. There were times when I forgot certain eye colors of characters and if I wasn’t vigilant could easily escape by my radar. Also I should mention keeping a list of technical details (opacity settings, filters, sizes, etc) is also a priority.
Gather all your resources together in one place. I have websites I constantly use throughout the Webcomic process (texture websites, sound effect websites, references for environments, clothing, poses, etc). I keep a log of them on an easy to find document. Remember organization goes a long way.
Staying on model is one of the most difficult things to do. Create model sheets for each and every one of your characters to reference. This includes head/body turns, clothing studies, style sheets, etc. There are countless ways of drawing eyes so document your character’s designs. Trust me when I say it is easy to forget without a reference. Once you enter into the robotic stage of your comic where everything becomes second nature it is very easy to accidentally draw different styles. The same goes for your environments. If a certain wall of a bedroom has two picture frames and a window. You want to make sure it will always have two picture frames and a window in those featured angles.
Create a swatch page/s of the colors that will be used in the Webcomic. This can seem like a daunting task, but its well worth it in the end. Don’t be like me and color pick from other pages when you can have variables disrupting the true color (i.e. gradients, textures, etc).
This would include files you constantly use throughout your Webcomic. As an example I have a file of a wooden texture that I have tiled to extend over a vast amount of environmental space complete with color range and filter.