Tip jars now seem as ubiquitous as peppermill stewards — who, come to think of it, may be the only members of the service industry not hitting you up for a single. But who deserves a tip, and who expects nothing more than his take-home pay?

The customs of tipping can be confusing. And while your cell phone may have a built-in tip calculator for restaurant bills, it won’t tell you how much (if anything) you need to spot the clown-faced contortionist who worked your daughter’s birthday party. Tippers and tippees across the country put in their two cents (or two dollars) for this guide to tipping everyone from parking valets to party clowns (but not waiters and bartenders — that you already knew).

Tipping for Personal Services

How to tip for personal services, from haircuts to takeout.

Hairstylists and Colorists

Average Tip: 15 percent of total cost.
Exceptional Circumstances: If a stylist conquers a last-minute hair crisis or fits you in on a busy Saturday, tip $3 to $5 more.
Things to Consider: In major metropolitan areas, it is customary to tip salon owners who cut your hair, too.

Salon Assistants

Average Tip: $2 to $5 for each person.
Exceptional Circumstances: If she gives you a nice scalp or neck massage, tip $1 to $2 more.
Things to Consider: Hand your tip directly to the person who did the shampoo or blow-dry, rather than leaving it with the cashier.

Personal Trainer

Average Tip: $50 to $100 upon reaching a goal.
Exceptional Circumstances: If a trainer often gives you a last-minute appointment or an extra 10 minutes, thank her with a small gift.
Things to Consider: Some franchise gyms discourage members from giving cash tips, so tip discreetly.