The People Who Care for Your Children and/or Aging Parents

Teacher: A small gift (not cash) from the child or a group gift with other parents and children, but check the school's policy first.
Nanny: One week's to one month's pay based on tenure and customs in your area, plus a personal gift.
Day care providers: $25 to $70 each plus a small gift from the child.
Night or weekend babysitter: One evening's pay, plus a small gift from the child.
Private nurse or home health employee: A gift (not cash), like a book or a potted plant.

The People Who Pamper You and Your Pets

Hair stylist: The cost of one haircut or a gift.
Beauty salon staff (manicure/ pedicure/ facial): The total cost of one salon visit divided among the staff members who pamper you.
Fitness trainer: Up to the cost of one session.
Massage therapist: Up to the cost of one session or a gift.
Pet Groomer: If the same person grooms your pet all year, give a tip that's up to one session's fee or a gift.
Dog Walker: One week's pay or a gift.

The People Who Care for Your Home

Housekeeper: Up to one week's pay or a gift.
Pool cleaner: The cost of one cleaning to be split evenly among the crew.
Yard and garden workers: $20 to $50
Residential building personnel: Superintendent: $20 to $80; handyman: $15 to $40; garage attendant: $10 to $30; doorman: $15 to $80; front desk: $15-$80.

The People Who Deliver

Newspaper deliverer: $10 to $30
Mail carrier: U.S. government regulations allow postal-service employees to accept gifts worth up to $20 each, but cash isn't allowed.

The People You Work With

Your boss: Don't give gifts, unless your co-workers decide to give a small group gift.
Your co-workers: If you are close with a co-worker and decide to exchange gifts, do it outside the office.

Your subordinates: A gift for your personal assistant is a nice gesture, as long as it's not too personal.

Who To Tip During The Holidays (AOL.com)