Straight letters. Simple is always better. Don't add to many extensions. Legible is better than anything.
Keep it simple. Keep all the letters the same size(height,width) How to do a lowercase E by drawing a line then circle it counter-clockwise.
Best advice is to never ask other writers for advice. Most are assholes. Do what you do and do it with style
Some of the best advice i have ever heard is don't expect immediate improvement, this shit takes a while to learn
best advice no one ever told me,... DO YOU AND FUCK THE REST style is style and we all have a different point of view when it comes to graffiti ....
Can't fake the funk in black and white. Helps you to focus on letters and develope some sick flows, also is good for your line work. Another plus is if you paint from a sketch I recommend keeping it black and white.
Do the outline quicker, so it doesn't drip. Use a fatcap for the white because that shit looks like a hot mess. Try some different lettering, just simple bubble-letters arent very eye catching anymore. start with the basic letters and play with them a bit. Make a LOT of sketches of a piece, trying something different everytime.
Learn by doing. if you wanna get good at graffiti than you have to paint, as much i love to sketch its not anything alike. start with the tag, do it ALL THE FUCKING TIME you will progress your letters if you focus on that and use that as your base for your piece. it will become more developed. the more you do it.... if that isnt obvious lol.
Stay original work on your style, originality is everything and pratice everytime you have the chance.