For me, I didn't know the exact specs I needed. I just wanted whatever worked in my laptop. Oddly, they have this down pretty well for cars. Whenever I am looking at automotive parts, it lets me know if it works for my vehicle.

If I recall, I wound up buying straight from crucial. They were the first site where I could type in what laptop I had and it would give me options for ram to buy.

It's a shame Newegg is rarely the place to go for actually good prices these days. I find I'm buying something like 80% of my computer parts from Amazon now as they consistently beat Newegg on the price of nearly everything barring some extremely rare (and randomly timed) substantial sale on Newegg.