How to get rid of makeup lines

I struggle to get the right shade of foundation on the first try.  If I am way off I will see if I can exchange it.  I feel bad taking it back when it was my fault, so if there's anyway I can make it work, I keep it.
When picking a foundation, I go for the lighter shades because I know I am very fair.  I have found a slight yellow undertone looks much better on me than a slight pink or orange or cool undertone.   I also have found that if I am having a hard time choosing between two shades, it is almost always better to pick the darker.  If the lighter shade looks like it might be lighter than your skin I wouldn't get it.  In the past when I have gotten a shade lighter than my skin, I look sickly.
If you get a shade that is close, but too dark, you won't look sickly.  You will have to do a little extra work to make the mismatch less noticeable though. Here's what I do:

• I apply foundation to my face
• I take a little more foundation (not very much) and rub it from my jawline to almost halfway down my neck
• You want this (on your neck) to be a very thin layer of foundation, so that you have a gradient between the bottom of your neck to your jawline.
• Take bronzer and slowly build it along the sides of your neck, next to the front of your neck, but not right on the front, sweep it all the way to your collar bones

You want to be very sparing with your foundation and bronzer application to your neck.  You want to slowly build it for a natural look.

Here's a video of how I do it.

Thanks for reading!! 

P.S.  If you do like high end makeup, Sephora actually has a color matching machine that scans your face.  I have heard mixed reviews about its accuracy, but it's worth a try :)