There are tipped employees, by IRS code, who are paid less by their employers because they ARE typically tipped. So they really do depend upon tips for most of their living. Even if they’re really, REALLY lousy, tip them something. Everyone has an off day. Tipping isn’t reserved for great service, it’s expected for basic service. A HIGHER tip is appropriate for excellent service.
That said, there are other professions in which tips are not expected (or shouldn’t be), but are fairly common. Housekeeping in hotels, that was a new one that came up in the mid-80’s. Taxi drivers. Movers. Let’s face it, folks, they ain’t making tons of money. They’re busting ass trying to scrape out a living. Tips are always appreciated. The carpet cleaning guy was shocked that I gave him a cash tip when he was done. I mean, it was only $200, so an extra $20 wasn’t going to break me. And it was a big house; took him a couple hours.
Back to movers. Any profession that doesn’t work for tips on a normal basis, keep it to 10%. If they do exceptionally more for you (not just some little extra that took no effort), then raise the tip according to your own appreciation of it. Like the doorman at a hotel when you go out, if he asks “Taxi?” and just whistles, and a cab pulls right up, that’s not worthy of a tip. Although you can, if you want. But if he walks down the steps, opens the cab door, or holds your luggage or bag so you can get in, that’s definitely worth a tip.
Movers. How many? Two? Go by end cost, not estimate. But $350, that’s $35 between two guys. Don’t get nitpicky at $17.50 each. Give 'em each a $20. If it’s only $250, that’s $12.50 each, not worth a $20. Give 'em each a $10. Hey, for $250, there wasn’t all that much to do in the first place. If it’s one guy doing all the work, give him what you would have given both of them.
Just as an end note, waitressing, long time ago, it was a basic 15% tip. Hasn’t been that way for 30 years; now it’s 20%. For standard, unremarkable service. For good service, go 25%, for excellent service go 33%. The 15% is only for hardly even there service, and 10% sends a clear message that she needs to just quit and find something else to do. And tip ONLY on the waitress’ performance, not the time or quality of the food. That’s the restaurant, out of the waitress’ control. Complain to the management about the food. Often they’ll comp it. Tip the waitress as if you’d paid for it, though.