Over the years I have used a variety of remote support tools from basic vnc to the built in Windows Remote Support tool. Below are 2 that I have found to be not only FREE but the easiest, and most useful.
Crossloop
Crossloop is a simple secure screen sharing service. Great for a quick remote session that is easy enough for Grandma to use. Here is a video tutorial.
IRemotePC by far has the most features of any remote support tool I have come across yet. Not only does it have file sharing service but you are able to sync folders as well. This use to be a 100% free service but now is worth the subscription and pay per use fee. Take a look at IremotePC in action with their free trial and you won’t be dissapointed.