How to Protect Myself from Scam on LocalBitcoins?

Hey guys. New here.

I have tried to use LocalBitcoins.net a couple of times. All the experience was offline and everything went smoothly.
But when I try to buy BTC online I get overwhelmed by tons of scam attempts.

How can one protect himself from scammers on LocalBitcoins? How to deal with Western Union? Can a WesternUnion transaction be reversed?

Thanks for your insights!

I prefer using exchanges for selling BTC. I have to pay much larger fees, but I feel secure.