Consistency is most important. Set rules about appropriate behavior, and don't back down on them because you want to avoid confrontation. Common sense ought to be used in how severe punishment is, but I recommend punishments that are beneficial to the household - for example, kids are fighting and hitting each other? Chores! Vacuum, clean, wash dishes. Do not use corporal punishment (no spanking, etc), giving chores are far more effective and help the kid "make up" for mistakes.
Support your kids' interests. Give them opportunities to explore new ideas and hobbies. Take your kid out into the community, to museums, to (age appropriate) movies. Support your kid's achievements and encourage them to challenge themselves.
READ. Take your kid to the library. If your kid is young, read to them every night. Make your kid read to you if s/he is learning. Read, read, read.
Do not use the TV as a babysitter. TV is a part of society, yes, but TV addictions are incredibly prevalent these days - set a standard and play outside with your kid, or play board games, color, anything. Make sure your kid does something that's physically active regularly - sports, hiking, whatever.
Finally: just be there, and love your kid unconditionally.