You don't really specify if this is for in person or online, so I'll give tips that I've learned.

The easiest way to show interest is sneaking eachother's eye contact. Thar is #1 to show interest. Try to make them laugh and (appropriately) try to touch them, both of these things will help get the message across and help ease them into showing any interest on their part. If they seem receptive, then keep eye contact, smile, and break eye contact to look at their lips or body to drop some more heavy hints. If they back away, then they may not be interested, but hey, you shot your shot.

Online, you can show interest by liking a couple pics and trying to start conversation, of course. Ask where they're from and if they're single to drop hints that you're interested.