What is the diff between bad and good?

Yeah, I think it's hard ordering on-line with DIYers. I would just say make
sure you have more than enough hair, a couple days after putting all my
extensions in I started noticing some spots I had missed in the back.

Otherwise, I put them in, then turned to a good friend of mine who is a
hairstylist (I hate when I dye my own hair or do my own hair extensions
then the people at the salon spend the entire time bitching to me about
what I did wrong or how dying my hair is bad and blah blah blah.) And
just asked him to match my color to the extensions to make it a little
closer, and to cut them so it blends with my natural hair. I was worried it
would look bad and fake, but I actually had people who had seen me a
few days before say stuff like wow, was your hair always that long? Or
wow, dying your hair darker made it look longer. I had to tell them I put
in extensions!! And I went from shoulder length hair to about the middle
of my back, I was happily shocked!

Goodluck, post pictures!!

Matching the hair texture

Color Matching

Length blending

Placement

Amount of extension hair installed