Agreed with above, go to a makeup counter like Estee Lauder, Bobbi Brown, Lancome, MAC, anything really, and get matched.
I'd recommend MAC, not because their foundations are particularly good, but because it is a very structured system and most people in the makeup community describe themselves in terms of MAC shade as a frame of reference. Once you know your general MAC shade, you can use this handy foundation matrix (
http://www.temptalia.com/foundation-matrix) to help you choose a color that may be a suitable match in another brand. The matrix isn't always accurate, but it gives you a great jumping off point.
If you buy a drugstore brand foundation, make sure where you buy from has a good return policy. Drugstores like CVS and Walgreens WILL allow returns on opened/used makeup.
In general, some tips are:
1. The best light to tell whether a foundation matches is to look at yourself in natural light.
2. You should always blend your foundation a bit down onto your neck so there is not a harsh line
3. If you have a foundation you KNOW matches you, you can always bring it in with you to the drugstore and compare things side by side!
4. Don't be afraid to ask for samples of foundations in department stores or Sephora. They are free and essential in picking the one that works well for you! For example, I got a sample of a foundation that matched me...but after 2 hours it oxidized and turned orange on my face! So, I didn't have to waste the money buying a whole bottle just to find that out and waste the time to return it.
5. Try to match to your neck, since you want your face to be the same shade as the rest of you.
I hope this helps! If you have any other questions feel free to PM me.
Foundation - Choosing the right shade
