First, if your institution has a style guide, follow its recommendations if there are any. But assuming it is silent on this point or you don't have one:
It's helpful to provide an outline of the rest of the report. If you have a table of contents already that might be good enough (I've seen TRs with and without TOCs). If you include something at the end of the introduction, though, avoid the "department of redundancy department" problem.
Bad: "Chapter 2, Methods, explains the methods of my investigation." You haven't said anything that wasn't already implied by the title.
Better: "Chapter 2, Methods, explains how we used the (something) method to (something)." The key here is to add something to "methods" -- name the method, say something about important factors for that method if relevant ("ran a trial with 4 groups for a 12-month period"), or otherwise tell people something about your methods right there in the summary. This lets the reader who already knows what the (something) method is to go straight to the results if he wants without having to wonder if they're at all valid. (An interested reader may go back and read your methods later, of course.)
So, more broadly, the point of a "here's what's in the rest of this document" section is to provide short hints that are meaningful enough to let people skim and jump to the parts they're most interested in.
Finally, the size of this short hint can scale somewhat with the size of the document. If your TR is 5 chapters in 30 pages, one sentence per is probably fine. But if it's 5 chapters in 300 pages, you might find it useful to drill down a bit and write a paragraph or so for each. Think of them like mini-abstracts for each chapter. As with an abstract, the reader question you're trying to answer is "do I want to read this?".
