Step 1: go outside every time he's outside. Bring a camera or a phone to take pictures
Step 2: stalk him. This should be easy, he's your neighbor.
Step 3: talk to the guy
Step 4: since you guys are now aquatinted. Hang out with him
Step 5: make sure there's no competition.
Step 6: start your flirting. Just don't flirt too much.
Step 7: confess your undying love for him once you two are best friends.
Step 8: love him more if he loves you back
Step 9: kill him if he doesn't love you
Step 10: TRY TO REPEAT!