To be honest, I've always felt that they key to staying in the lower regions of the top 100 is to get a couple of soft first round draws in Grand Slams and other big events and take advantage of them. This was something Bally always did throughout her career, with probably only two exceptions - Klashcka (although that was long before she was top 100) and Martic (where she choked but then made up for it by beating her at the US Open). Anne was not so good at that (losses to the likes of Mayr, Scheepers, Dolonc etc...) but generally far better week to week on the tour, and it was ultimately the nail in Katie's top 100 coffin (although she beat Mayr in Oz, she lost to Craybas at the French dropped out the top 100 and kept sliding backwards, and had a couple of other winnable matches at Wimbledon over the years she couldn't get through).

Obviously you can still get into the top 100 just by tearing up 25's, 50's and picking up the odd tour win, and winning a couple of GS matches alone won't get you near the top 100, but if you can avoid getting lumbered with mandatory 10 scores and have 70s on there instead it makes a big difference when you get to the 80-120 range where there's in reality little to nothing between the standard of players.