Here are some tutorials and tips and howtos on specific topics that are always difficult to master.

I recommend that you take advantage of them!

VLOOKUP: http://office.microsoft.com/en-us/excel-help/results.aspx?filter=1&ck=1&av=zxl140&qu=VLOOKUP

PIVOT Tables: http://office.microsoft.com/en-us/excel-help/results.aspx?filter=1&ck=1&av=zxl140&qu=PivotTable