making potential new friends

Question: Before I ask for another person to be on my Friend's List or vice versa, I usually send them a message to show that we have something in common: BUT NOT ALWAYS.  I think that I ask someone to be friends just to see if they are interested, maybe a real friendship will happen - or maybe it won't?  Tho prefer to have some idea why or atleast recieve a polite 'no thanks' either way I am generally not offended if someone turns me down or ignores me: just wasn't meant to be, right ? So , my question to everyone here is : How do you handle making friends ?  Do you ask first or message them first ?