Use the enviroment and Give player objectives... Help?

Not too long ago I made a post asking for high level combat. I know the basic drill about monster CR, and resource management etc. It is not being enough. One of the comments that stood out along a couple of others was Use the enviroment and give players objectives. Ive seen this a lot and I've tried to put it in practice but I just feel like I am not good at it! Do you wonderful DM's of Reddit have examples or ideas on how have you applied this effectively?