If applications run slow and the network is slow to respond especially from remote locations? what to do?

This can be due to many things. I would check the network connectivity and bandwidth analysis first. It depends on how the applications are coded as well. One thing I have seen in my experience is that the web / application coders are not experts in networking typologies and concepts and sometimes poorly coded application can cause serious bandwidth and performance issues. I would use a monitoring proxy and analyse the traffic to identify the root cause of the problem.

Since you mentioned remote locations make sure you have enough bandwidth / QOS for the services you use.