And actually fly what they tell you to fly. Then debrief them after the pass, if able.
A lot of guys shoot practice PARs VMC and either consiously, or subconsiously visually line themselves up on the runway. The controller gets no training out of it and thinks that he's got it wired, when in fact, he's misreading his scope and doesn't know it. From what I've seen in the radar room, giving a good PAR is as much art as science.
If you trickfuck the system and do their jobs for them, the next time you hear his voice may be when he's certified to be on his own and you're going down to mins. If the approach sucks it might be as much your fault as his.
Every now and then they may even ask you for some weird stuff. I was shooting practice PARs in the PRCP (the acme of east coast tactical flying), and the supervisor came up and asked me to fake a lost comm issue after I turned dogleg to final. It was VMC (night), and there wasn't anybody else out flying, so I did it. He spazzed out at first, but got it together and handled it pretty well. I think it was his checkride or something.