If you have a problem that you can document that you're seeing with memory, it'll be possible to help. Otherwise, there's very little you need to do with memory on your server. It's largely managed by SQL Server itself. A few options you have for managing memory, optimize the application workload (tune the queries & processes), allocate more memory to SQL Server, switch to 64bit if you're on 32 (better and more memory available), if you're using 32bit and you have 4gb of memory you can use the /3gb switch in the boot.ini to access mroe memory for SQL Server, PAE memory beyond 4gb can be used in SQL server again by modifying the boot.ini.

That's about it. The most important thing you can do is write your queries and manage your processes such that they work well. After that, let SQL Server manage the memory for you.