Depends on the friends were out with. I have a few friends who do very well and like to splurge at restaurants. We were at a nice sushi place in NYC earlier this year with one couple and the tab was $450 pre-tip. $320 of it was their food/drinks. Needless to say, I'm not splitting that.
For normal meals out, where the tab is between $80-$120 for two couples, I'll split it. I pick up the tab if it's a reasonable meal and friends are visiting from a good distance (a flight or a 3+ hour drive).
I hate tipping with a passion (the workers deserve to be paid by the owner, not by patrons) but tip very well. I usually calculate to 20% and then round up even more. The one trend I can't stand is bagel/coffee shop/food places that don't have table service asking for tips on the tablet checkout systems. Seriously? You're pouring my coffee and handing me a muffin from the display case; I'm not adding 20% on to my tab for that.
That is my rule: it has to be table service to get a tip.