An infection after a Tattoo is not common however it is possible especially if correct aftercare is not carried out. Here's some advice on how to prevent it and what to do if an infection occurs.
Step 1: Choice of Tattoo Parlour and Tattoo Artist
If the cleanliness and sterilisation standards aren't acceptable go somewhere else. If the standards are low and you go ahead with getting a Tattoo you're almost asking for infection some of which can be very serious such as HIV and other infections that you really don't want.
Step 2: Aftercare
Be sure to follow the advice and instructions that your tattoo artist gives you. If you're unsure of anything then ask. You should also put some kind of healing ointment on your tattoo at least twice a day such as Bacitracin Zinc, A & D Ointment, Petroleum or Neosporin.
Step 3: Clothing
Wearing clothes that constantly rub up against your tattoo it can irritate it and cause it to get infected. Wear loose clothing and be sure to let fresh air get to your Tattoo whilst it's healing.
Step 4: If Tattoo is Infected
Signs of an infected tattoo are pain and redness around the tattoo a few days after having it done, swelling, heat radiating from the tattoo, any discharge that is cloudy, yellow or green and a fever. If you think the tattoo is infected go see your tattooist and if they agree then see your doctor.