The honest answer: You Can't! But let's face it. We are going to wear flip flops or sandals or some sort of foot fashion that women will poke fun of. More than likely, your own friend will make fun of you too. Don't worry though, he will soon wear Mandals for you to make fun of. However, there are occasions where Mandals are perfectly acceptable. Places like the lake, the beach, or in the privacy of your own home are all places where Mandals can be worn without looking bad. Places like dates (unless on the beach), concerts, and going out to the bars with your friends are places where Mandals are not socially acceptable. Let me shown you the two pairs of "Mandals" I own.
The Chaco: Now this is my mandal of choice. It is adventurous and durable. I have worn it to the lake, the river, and even fishing. This particula mandal I find acceptable to wear when you go out grocery shopping or somewhere where dressing up isn't necessarily required. Going on a long road trip? Throw these bad boys on and hit the road Jack!
The thong: Now mine is all tan, but this is pretty much the model that I own. You can see here it has a nice rubber sole with a good nylon/leather strap. You want a thong/flip flop that looks durable and made to last. Stay away from the Old Navy $2.99 rubber flip flops. They make you look too cheap.
What mandal are you rocking during this beautiful weather?