^ Best money comes from the schools themselves. Most fastweb/etc. scholarships are lottery-like. A few are worth your time and could be useful to replace your student contribution, but they won’t cover larger costs.
The scholarships offered by the sites themselves are a waste of time. The scholarships listed from real organizations, though, can be useful. I have a scholarship from the American Chemical Society which I found listed on Cappex, for example; it’s a small amount, though.
Do not be overly concerned with getting outside scholarships unless you are eligible for big ones like Gates Millennium. Focus on schools that will give you full aid. Run the Net Price Calculator to see your costs for a variety of your instate schools. Make sure to have backups as well as competitive schools. Also look at the ‘meets full needs’ private schools, like the Questbridge partners. (note Questbridge isn’t a scholarship it is help getting admission to schools that will pay your full way.) After you have figured out what you need to do for applying to colleges that will give you great aid, then look at outside scholarships as time allows. Outside aid is often for a one time smaller amount. While every bit helps, you won’t likely get enough to pay a 4 year school that way.
I meant to add, the way you ASK for a scholarship is to APPLY. Read the directions on the website and follow it.
Also keep track of deadlines. Some schools have early deadlines for applications if you want to be fully considered for all scholarships. Some schools will also have separate applications for some scholarships. The school’s website will usually have all this information.