There are privacy settings that you can use to limit what is seen by people other than your friends. I know from someone trying to find me via my email address that they couldn't since I have that set to be viewed only by my friends.

I generally ignore friend suggestions unless they come directly from other people on my friend list. Those show up in the same place friend and other requests are. I've also limited the apps I use.

There's been a virus going around that once it infects an account it will message other accounts with supposed you tube videos. I delete those out of my FB inbox without even opening them.