Make up some business cards and keep them with you. When you see a tree service working...come back when they are on a break

, and ask who is the boss. Give him your card and tell him your intention, thank him, shake his hand and then get back out of their way.
If you live in town, get to know the city street dept. guys, they work by the hour so they have some time to talk usually. If they don't do their own tree work ask who they call and say that you would like to meet that service next time they call them. Explain to them you can save them some labor/gas by having stuff dropped in your yard instead of hauling them back out of town (have a good idea of what you want and let them know, or you will get trash). If you live in the boonies go to the township road shed and ask about what they do with their trees, I don't know your geography but around here they remove alot for drainage/storm damage/easement...
The local rural electric company also remove trees for easement (and pull old cedar/SYP poles if you are interested). The biggest supplier for me are excavation contractors doing clearing work for new housing developments/drainage/bridge construction. I called all of them on the phone to get a feel for their attitude, most where indifferent but there are alot around so 1/20 is still enough to make it worth while.
As far as pickup or delivery that depends on the situation you have to be flexible.
Most of mine are delivered, but that was 1-2 years in the making. Plan on fetching some getting started, if it is a good one you have to be prompt "you snooze you loose" and if the source calls you a couple times and you are a no show...they won't waste any more time with you.
Pay them back, buy a good chainsaw sharpener and learn how to use it. A handful of sharp chains can bring a trailer load of logs. After a hard days work some guys like an adult beverage, whether you partake or not a 12 pack usually will bring a crew with some logs to drop and something to quench their thirst, and spend a few minutes talking (the most important part, getting to know you). They could take their logs to the dump/split them for firewood...or drop them at your place, have a cold one and if you are on their way save a couple miles and get them home quicker. Most tree services chip all but the kinda logs your mill can handle, might as well drop them with you.
I can offer more advice later and am sure others can too, that is just stuff off the top of my head and I am a little tired from sawing a load of sugar maple, ash and a couple small cedars the city street guy dropped of yesterday

.