To start with Spiders don't have very much knockback so they will attack relentlessly so you want to keep your distance. But what I do is I build a little box and they will climb on the roof when they are up there break one of the roof blocks then climb up to where your head is at the top of the roof then you can hit the Spider because they can only go down a 2x2 hole and when it is one block they won't fit now they will probably fall off the roof when that happens make sure to lure them to the roof once again. PS: This won't work with Cave Spiders because they are much smaller and can fit in a one block hole.