I’d start by looking up what knot your character should be using, and researching how it’s tied. I’d also recommend actually learning the knot and trying it a couple times. Knots are designed for specific jobs, so finding the right one is important for authenticity if you’re into that. It’s also not a dangerous skill to practice, so if you really want to know how it feels to tie that knot, there’s no harm in learning it.
A quick web search turned up http://www.animatedknots.com/, which appears to be a good reference site.