What to wear: Something you feel comfortable in that reflects well upon who you are and how you want to be perceived as.
You should always be reasonably well-dressed, and here's why: You're giving off signals about yourself to everyone around you, and one of those people could be your future better-half.
You want to seem like yourself, and definitely someone that can be dated. It's unfair to tell someone: This is how you should dress all the time, so we'll leave this one up to your own interpretation. Just be conscious of the signals your clothing is telling people you're attracted to. If you shirt reads, "FUCK," there's a good chance they're not going to take you seriously.