ok, here are some real tips.
Playing:
1) Understand the Rules - If you don't you'll annoy people to no end. Tons of questions are not fun to anwser, unless the mod is a jerk (like me) and put in something new that you shouldn't know unless the mod told you, or you hacked their account. If the latter, Shame on you.
2) Always look at the rules for new rules - DO EEEET! I know you newer players and even us vets, can get lazy and think they are the same. THEY AREN'T ALWAYS! Just look for new rules and read them. It can save a lot of trouble. And a lot of frustration later in the game.
3) Never doubt the mod. Easy to understand. The mod should know the most about the game, so the chances are they are right. NEver continue an argument to far. Ask for clarification.

Unless the mod is someone scummy (like Mandy) or a jerk, then DOUBT ALL YOU CAN!!!!!
4) Read old games - When your new reading old and going on games can really help. Also they'll improve your mafia resume, as from my experience the people who read past games turn out to be the players I'd put on the good list.
5) Never trust Mandy - Cause he's always Scum.
6) Don't join too many games - This may cause to you deadbeating in some of them, which sucks, especially if you're like me. Only join the games you can handle.
7) Always follow Fircoal - Cause he's always right.

No Lynch is a no go. - I remember when back in the day, it was being debated about the useful of it. But now it's a pretty one sided, it's bad. You need the info from the lynch, don't try to no lynch out of it. Except in dethys, but that's a different story totally
9) Most importantly, have fun. These games are for your enjoyment.
Modding:
1) #1 most important rule of modding, you must care about your game. IF you don't it WILL be a failure. Believe me, the 3 games I gave up on became failures, 2 of them close to premature death. Another game got lucky, but I did end up caring again.
2) Only mod when you can. - NOthing sucks more then a mod that quits the game. Make sure you can mod when you do.
3) Not too many games at a time - Don't spread yourself out.
4) Balence is key - What MAndy said above.
5) Again, read games to see how people Mod. Ask for help to mod. Sure there would probably be someone willing to help. Have patience.
Well that's all I got at the moment, if I think of more, I'll add it to this post.

(And maybe make a new post with it.)