Showing the header in a SSRS Report without overlapping
I created a report for my user in Reporting Services 2005. The report was a very simple matrix, but the problem I had with its header could have just as easily existed in a table. Having a lot of rows and columns in the matrix meant though that when my user would scroll through the matrix, he couldn't see the headers for the columns and rows. So obviously I had forgotten something...
I went into the matrix properties and went to its Groups tab:

I entered each and every one of the groups and defined that the Group's header would always be visible:

I went back to my report and saw that wherever I scrolled I could see the header, but it wasn't at all readable as it would overlap with the data rows:

(The problem existed whether you were scrolling down - and then the column title overlapped, or if you were scrolling to the side - and then the row title would overlap).
So what's the missing part you need to do?
Well, it's pretty simple. All there's left to do is color the headers! See, the fact that the default background property for the table or matrix is "Transparent" really makes the overlapping happen:

Microsoft must have secretly wanted us to style the reports we create because giving the headers some color makes it all readable:

(If you notice, both this and the previous example show the title above Adam Barr - only this one is readable)
So don't forget to style your report - it may end up helping you see the header of your report.