A simple "thank you" or "thanks" is usually perfectly sufficient as a response. If you think they are using the complement as a means to initiate conversation, it might be good to say something more about whatever they are complementing. Example: "Thanks! I got this bag in Australia." Hope this helps :)

A more informal way to say thank you is to use the word 'cheers', in British English it is universally accepted as 'Thank you' in those situations, but you wouldn't want to use it in a formal meeting or interview situation.

You can say "Thank you" or "Thank you so much" or however you want to thank them. You can also add in something to show humility or you can give a similar remark about the other person. If some one praises your clothing and you can praise something they are wearing as well. If someone praises your performance you can add in something like "I'm glad you liked it"