It was really obvious which lines were standups, they were the lines with the evening showtimes & early morning finishes. Also where it shows what the line is worth, they were the lines that were only worth around 30-35 hours.
As for relief lines, in the bid pack these lines showed up as lines at the very end of the bid pack, and had no set days off and no set value. You bid these lines last (usually) because you are bidding blind. A relief line is better than reserve, but you don't know what you're going to get. After the bids are final, your relief line is then constructed out of trips from people's vacations and various other trips that came open for whatever reason. You can send messages to crew planning before your relief line is finalized asking for specific days off, if they're in a good mood they might give them to you. It can be a pretty sweet deal, some guys have gotten good trips that way, but again, you're bidding blind not knowing what you'll get. But it is better than reserve!
The only time I ever bid a relief line was when I was a very junior line holder and I needed a weekend off to be in my brothers wedding. I sent a very pleading message to crew planning telling them why I'd bid relief & to do anything they wanted to me for the rest of the month but to please please pretty please give me the one weekend I needed off. I got the weekend off, but damn the rest of the month sucked!