Tipping confusion

[revots33]

All these tipping rules are ridiculous IMO - why do we tip a gas attendant who pumps your gas, but not a supermarket cashier who bags your groceries, for ex.? It makes no sense to me. But I don't want to be cheap either. I just don't want to be the only sucker going around tipping everyone who ever comes to my front door. Is there some sort of master list to follow about who to tip and who not to?

Any thoughts on whether or not I should be tipping these people?

Guys who deliver a TV I ordered online?
Landscaper?
1-800-Mattress delivery guys?
Plumber who replaces a leaky pipe?
Electrician who installs a ceiling fan?
Guy who installs DirecTV dish?
Contractor who re-paves driveway?
Furniture delivery guys?
Trash pickup guys (public works, not private)

Apologies if some of these are obvious, I'm a relatively new homeowner and have no clue if I am stiffing people who expect a tip.