I went to one of those places that sells salon products the salons as well as the public and bought what I needed there.
Mix the product and use the straight end of the comb to go in and out and pick out very thin pieces of hair. Put foil under those strands you've picked out and put on the highlighting cream and fold it up nicely. Do many along the "top" part of your hair and use clips and do some underneath...depending on if your hair is layered or how it's cut, about 20 "foils" are usually enough. Start at the front and work one side of the head, then do the other and try to do it similarly and leave the back. Don't do TOO many the first time or you'll end up "all blonde".
If your hair is shorter and layered, remember to work down and make sure you've gotten strands from everywhere. The "top" part of your hair is the most important because that is what shows but remember not to overdo it. Don't be too "straight" in doing your hair either...or you will end up with that "row" of highlights which looks unnatural...you want it to be sporadic and not systematic.
If you are not sure, do just a few, and then you can go back and add more the next day, or in another few weeks.
I prefer the blonde type streak rather than the brownish ones (I have dark brown hair) as they look very nice when you use a straightening iron. The other ends up looking reddish which I don't like.
If you use the products you buy in stores, just do the same...do little streaks all over the top part of your hair where it's visible, then work some streaks in under and in between.
DON'T make big wide globs unless you like that "chunking" look...if you are looking for soft fur like looking hair...the thin streaks look gorgeous, especially with the straight iron look.
If your hair is TOO streaked start over, die it brown or whatever and then in a week or two put highlights back in. I don't like touching up outgrown streaks...you always miss a few here and there.