My most recently completed WOD was Invoice1 and it was fairly difficult. I attempted it three times, with my final and best attempt being 19 minutes and 54 seconds, which barely gives me Rx time.
Invoice1 required that we create an invoice that contained five different products. And through the use of variables and expressions, compute values to get a total.
The only thing that really worked well for me was my previous experience in programming in Javascript. Although it was three years ago, I vaguely remember certain details. Also, W3schools tutorials helped immensely. However, what slowed me down was not having a game plan or any kind of strategy; I kind of just went for it and encountered a lot of difficulties from not having a plan.
For my next WOD, I would definitely have some sort of strategy before I start, and try to read the directions more carefully.