What size tattoo needle do you use for outline

on average a three is used unless you are doing portraits and then id stick to a one. for larger projects a 5 is okay always make sure you are using a round liner for outlines.
I disagree a 3 liner is best for small details. Most novices start of with small tattoo needles just due to being misinformed. When i started i used 5 round tapers and i always found myself going back over lines. in my opinion and what I use know are 7 round liners they lay down a nice semi-bold line that is just right. if you need to accentuate a line a bolder just do your fills with the same tattoo needle. My art improved ten-fold when I switched from a 5 to a 7. point is too they hold more ink too. The trick to good lining is holding your machine upright to the skin , go slow and do as much of your line as comfortably possibly. maintain your confidence.

I agree with the second poster. I am a tattoo artist who never did an apprenticeship anywhere. Just bought a machine from an artist friend of mine and starting plugging away on Pig skin. Lining is the MOST important part of a tattoo. Without a solid outline, there is no reason to color, shade or fill. So get a good line. Make sure your liner machine is well tuned, running well, and not misfiring. Next choose a 7 round or even higher if you are doing large work without alot of details. Then GO SLOW. Remember the machine moves fast, but you cannot move faster or you will end up with a dotted line. Tattoos hurt, don't try to be the nice guy and compromise your work to keep the client comfortable. Go as slow as you need to and allow the machine to do the work. Keep the ink flowing. Do not ever allow your liner to run out of ink. You will end up with line that you will have to go over again causing more pain and potential scar on the tattoo. And lastly, practice. If you are new to tattooing, do NOT try your skill out of a human until you have a handle on how the machine works, etc. Buy some grape fruits, honey dew melons, pig skin (from a butcher) etc and start to practice. The practice skins on eBay are garbage. They do not accept ink nearly the same way as real skin and you will end up frustrated. Plus there are very few places on the human body where you will be working on a "flat" surface so why practice on one? Good luck!