I've got numerous tattoos, the latest of which is still a work in progress. It's a large phoenix, head is on the front of my right shoulder with little tendril things up my neck, one wing takes up nearly my entire right upper arm, and almost full back. All my tatts can be covered with regular clothing, depending on the collar I may need a scarf to cover all of the bird.
A couple of things to consider:
Size of the tattoo. More detail needs a larger tattoo - they can be scaled up or down to some extent, but a detailed small tattoo will blur over time, and that detail will get lost. So consider carefully how big you want it to be when you decide on the design.
Colour vs monochrome. Personal taste, and obviously depends on the design. Some tattooists have preferences and only do one or the other.
The tattooist. Check out their work. Most places have books of flash, plus photos of previous work. Check out the work before you decide who to book with.
Body area. Some tattoos are designed for specific body areas, and look best on those areas. It's possible to get a custom design that works around a body part (or parts) like my phoenix.
Body area for visibility. Do you want it covered most of the time? Are there times when you'll want to flash it?
Body area again, for the pain factor. Bony areas tend to be more painful than more fleshy areas. And the more sensitive the area in general, the more the tattooing process will hurt. I found the neck part of my birdie excruciating... the tattooist said I was very brave, considering he'd had an outlaw motorcycle gang member tap out when he was doing a neck tatt on him!
Body area again (!) for aftercare. You will need to be able to reach the area to apply cream for 1-2 weeks. Can you reach the area, or do you have someone who can do it for you? Also, with some areas, clothes rubbing (eg bra straps, jeans waist-line etc) can make the healing process a tad uncomfortable!
Future tattoos. Tatts can be addictive, so if you think you're going to end up with more than one, think about the placement carefully. My bird has a wee green frog nestled on his back - the frog has been there for years, so the tattooist worked him into the bird. At the time I got the frog, I wasn't intending to get more tatts, so shoulder blade was just fine.