Step 1: Find Your Style
Should my script write left to right? Or top to bottom?
Will I have the same amount of symbols as the number of letters in your Alphabet, for example English has 26 letters, same number of symbols? Or a couple of symbols that stand for the same letter? P.S, doing that really screws people who try to break the code.
Are your symbols going to be broken, or all one continuous line (like mine).
Are you going to use a symbol for spaces between words (which works best for systems that are all on one line, again you'll see what I mean when you look at those pictures.)
Are you also going to to make a number system (P.S its pretty hard.)
Step 2: Make the Characters!
Tips to keep in mind, keep all your symbols distinct, and try not to let them blend together. One a single line system I leave a segment of straight line to help break the different symbols apart. As you can see by this photo, it takes quite a bit of brain storming, to get everything just right.
I decided on long flowing characters, that look confusing but are really quite organized. Also I made characters for spaces between words, apostrophe, and periods.
(P.S. I had to remove some part of the picture as they were the Alphabet and no one must know my secrets, BUWAWHAHWHAWHA!!!! Cough... cough... hack...)