Travel plans should be made for holidays and keeping in mind the atmosphere and seasons you like. If you are having a family you can have a discussion with them as they will also suggest places to visit which you may have not noticed while planning the holiday.
If you are going with your friends you can have a discussion with them too, and decide a place and time to go on. There are days when flight prices are down and you can make use of them by getting tickets on cheap prices. For this it may take few hours of your internet surfing.