Tables don't have performance. Queries have performance. Asking how to improve the performance of a table is meaningless, what you need to do is improve the performance of queries that run against the table.
Table size is not necessarily related to query performance. Large tables can have queries that perform well. Small tables can have queries that perform terribly. What you need to do is identify queries that need tuning and tune them.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability