Don't move up in corners until you actually know what you're doing. Most likely you'll just end up corner diving like all the other morons yelling "inside." My response to "inside" is generally to do nothing at all, it's not my job to leave space for them just because they don't know how to ride in a pack.
Move up when the pack slows. Learn to fill gaps. Pat attention. If you're not moving forward, you're moving back. There are few other tricks that can be explained on the internet.