Are several small car parks as you drive around the commons, we parked in the one one Lea Coach Road which had space for around 10 cars.
Few hills but nothing crazy. Was quite muddy in sections with mix of muddy woodland paths and sandy heath paths. No stiles.
We went in wet season with lots of large muddy puddles and couple of small streams so enough to make the dig wet and smelly, but no real water features here
Poo bin in the car park
*Postcode takes you to another car than the one I used, I went south a bit from there and then right along Lead Coach Road finding another car park.
There's no real discernible route that I can recommend, it's a fairly large common (or two commons separated by a road) with lots of paths and routes so we just set our GPS so knew how to get back and just ambled around until we wanted to come back.
It is pretty busy, and there were lots of other dog walkers and the odd cylist despite seeing signs for no cycling! There are warnings of cattle too but we didn't see any, there are fenced off areas which I'm not sure are part of any preservation projects or if were for the cattle but that didn't disrupt our walk and still plenty of space to explore walking around them and taking in some very pretty scenery.
I wouldn't recommend this as a completely off-lead walk though if you're not familiar with it as quite often you'll be walking and realise you're not too far from a road, and towards the western direction you can hear when you're getting close to the A3 which runs alongside the common.