1. Don't take risks, they might alienate viewers - nevermind that the risky plotlines might be interesting, and even endear you to fans and other discerning viewers. Keep it simple and safe, ultimately harmless and boring. Executives will love you for it, until the ratings drop, but then you can do some "extreme" stunt to pick them up, like a partially nude scene or gay kiss that will never be mentioned again - that's the only time you really want to take a good risk.
2. If you deal with controversial topics, make sure to miss the point and stay shallow. Let the viewers draw their own conclusions at the sacrifice of good characterisation - characters don't need to have a strong opinion on the matter.
3. Despite not wanting to take risks, always consider killing off a character or dropping their plotlines down a little, to keep people on their toes you understand. It creates a sense of drama to randomly change someone's status, just remember not to mention it too much afterwards, incase it's a sensitive subject - you don't want to trigger the floods of grief so better to pretend they never existed and nobody really cares past the end of that episode.
4. Focus on the main characters, and by that we mean the main two or three. Even if the regular cast goes beyond that number you'll want to go with developing the key people first - the rest will come later, when you have time. Oh my, the world of TV is very busy, you say? Ah well...
5. If people start to notice the lack of development for any characters, just cram as much as possible into one episode. That'll make up for last few seasons without. Don't worry if you go over stuff you've already covered - it's still about them so it's all good. Failing that, kill them - it's the surefire way to stir up a passion for them. ;)
6. Use recurring characters, the more the better, even if they never actually do much recurring, nor any speaking. Simply having them on screen once is good enough to create that diversity people like so much, it ups the realism you know. But make sure you refresh the recurrings every season to keep it feeling up to date, you don't want the show to get stale!