[Heavydrop]

When I was a lower level and just got my ports it was a great way to make money so I did it.
Tipping or paying for a port is just part of the way things are and unless you want to be put on a "no port" list somewhere (yes, I do have such a list) it is in people's best interest to offer something reasonable as compensation.
Now that I'm higher level I don't need the money from ports so much but once in awhile I'll do it. My rule of thumb, as has been mentioned, is that if I am non /anon and you can see my class/level etc. then that means I am open for business for porting. I am available for ports. If I am /role then it means I am busy soloing/grouping/camping something and I don't have the time or interest in porting. If you know me in game and I can come help I will but most of the time I'm not up for it.
Tipping and tipping well is logical if you can afford it. I port those in need as well I just might not feel as inclined, but I will still do it