Confusion Tactics
Does the person you're talking to have a shorter attention span than you? Well, all you have to do is spout a roundabout story about something that has some relation to alien life, and cap it off with a spontaneous "Don't you think?" They'll just smile and nod, you'll feel that much better even though they're just pretending to agree.
Mumbo Jumbo
If you know the person you're talking to isn't so much into science, you can spout of some nonsense that sounds all scientific. A quick example: Due to the molecular structure that must conform to the nucleic acid of the cellular osmosis process, Martians are green. This method is based (remotely) on real science, and allows for the final method.
B.S
Keep in mind you'll need to be creative for this one. Combine all of your scientific knowledge on aliens, which you have absorbed from George Lucas and the X-Files. Then, you can use your "expertise" to prove that E.T did indeed phone home and William Shatner does have a phaser rifle in his closet. It doesn't matter whether those shows are "fake" or not. Besides, they're probably proof enough to you if you've bothered reading this far!
