It's not about you or your friends. Don't play and play and play if you have performers lined up. I've seen hosts do that only to have fewer performers the next week. Think of it as giving back to the music community. The less you play means the more success the night went.
Ditto on the time or number of songs. Try to smile when people are jerks. You will have that guy who thinks he deserves more time than anyone else because he's better. He might be better, but don't give in. You'll also have people who whine that they brought followers to hear them...so they wanna play earlier, even though they didn't get there early enough. Often times their followers aren't even spending money to support the bar. Make them wait their turn. Letting people skip over others who've been waiting shows you're not attentive or caring enough.
Tell everyone to tip the bartender. Say this on the mic. Say the bartender's name.
Introduce each act. Compliment the acts. Don't criticize or offer comments that may come off as negative...unless you're asked...and then keep it to the minimum.
Treat everyone equally.
Promote through word of mouth, fliers, facebook, craigslist, etc. Get people in there.
Enjoy it while it last. Even if it's a success, it's a huge headache and you will get sick of babysitting.
I just did an open mic for very little money. I quit when the bartender quit. The new bartender hired someone else to do it and asked me if I wanted to co-host. I don't know the new host and not sure how he operates...so that in addition to the prospect of no money, I said no.
Good luck.