The best way that I can think of (coming from downtown) is to take Main Street past Clark University until you come to where Cambridge Street comes in from the left, DO NOT turn there, but take the next left (you should see some electrical transformers/wires at the turn). I don't remember the name of this street, but it will take you straight under some railroad tracks and then to Hope Cemetery, which will be on the left. If you are coming from Southbridge Street, you can turn right opposite where the old YD diner was, and you'll cross some railroad tracks and soon see Hope Cemetery on your right (you'll have to turn right at the next intersection to get to the entrance).
I've got two grandparents, four great-grandparents and a bunch of other family in there, so it's a place that I go to without having to think of the directions (which is why the street name escapes me).