Restaurants: Usually the base is 15% for me. If you suck, you get 10%, maybe 12%, depending on how much you suck. The absolute lowest tip I ever left was $1 and change on a 24 or 25 dollar meal because the waitress took our order, brought our food, and gave us our check. And never came back any other time, and was really unpleasant those few times she did talk to us. If you're really nice, it's usually closer to 20%. If I've been at the table for a really long time, I usually throw a bit extra in for that, too.
Bars: I start off giving high tips, like a dollar or two per drink, to make sure the bartender always comes back to me right away, and then slowly lower it by the end of the night. Or, if I have a tab going on my credit card, it's 15% of the total if you're nice and attentive, 10% if it took me forever to get a hold of you or my drinks sucked.
Tip jars: Never tip in them.
For delivery: Usually 10%-ish. This isn't an issue anymore as of last week, but my boyfriend and I used to have a rule that the delivery guy got an extra 2-3 bucks if we didn't have to walk downstairs to get our food. We didn't have a buzzing system at our apartment building, but there was a security code panel, and since it was a huge building there was almost always someone coming in or out. Even in the middle of the night, the Domino's guys (and a couple other places) never had a problem getting upstairs. So we knew it could be done. But if the guy just sat in his car and called us to make us come downstairs, he would get the bare minimum.
Salons: This is where I vary the most. It all depends on how much I like what's been done (which kinda sucks for hair stylists because I am really picky about my haircuts), and also how nice the person was to me. I usually give somewhere between 10-20% for haircuts, manicures, and waxing.