It's a complex topic and there is no quick win.

Triggers will likely be a performance disaster, forget about it.

Trace could help, but again could turn into a performance nightmare and/or huge waste of disk space.

Extended Events will likely help, but support in 2008 is very limited. I wrote a blog post on the topic that you can find here: http://spaghettidba.com/2015/04/20/tracking-table-usage-and-identifying-unused-objects/

The idea behind is that you can use Extended Events to capture reads and writes to a table and record them to a target table. I have no idea whether this could end up working in 2008 though. Sure thing, it won't work as it is, you will need to rewrite parts of the code.

Good luck!