Best bet get there early mate. I usually park up the hill just past Wadsley Bridge. There are a few units up there with secure parking.
Only problem with getting there early is nowhere to drink as all 'home' pubs and having to sit and look at their crap ground for ages!
Depends how close you want to be If you don't mind a walk, Wadsley Bridge WMC is £1 - £2 ish. There's street parking round there but don't leave anything of value in the car. Same on Fox Hill Rd - free parking til the police start putting cones out 15 min walk (parallel to A61 runs between Grenoside & Hillsbro). If you want to get closer, there's Clay Wheels Lane turn right at bottom of hill next to Carphone Warehouse. Also some pay carparks on Penistone Rd. If you pretend you're going swimming there's Hillsbro Leisure Centre (fre but they do have a man on checking if you look like footy fans).