How to speed up a multiple select query
It's quite difficult to give any suggestions based on that information, but here's the approach I normally use for performance tuning. The order of different steps can vary, but these usually give quite a good idea where the improvements should be done.

1) Check for blocking

if someone else is blocking the query, you should focus on the blocking query first

2) Set statistics io on. 

This will show you the I/O count per table per statement when you run the procedure. If your sql is simple statements, I/O count and time spent in that table should be quite linear. Amount of data in cache makes a big difference for first vs. second run. If you're using user defined functions, I/O generated by those is not shown with statistics io.

3) Query plan, preferably actual plan. 

Look at think arrows (=a lot of rows). There might be something to improve here, indexing, statistics, something to adjust in the query itself. This should be give similar picture as statistics io.

Key lookups, especially ones with big percentages or big actual execution count. If the number of output columns is small you could add include columns to the index. Remember, percentages are just estimates. 

Look out for index / table scans, especially in cases where you're not reading most of the table.

4) Plan cache.

You can find statement level statistics from sys.dm_exec_query_stats. I usually look into total_worker_time and total_logical_reads, other columns can also give valuable information about where the problem could be.