The Martian is in Woking town centre, next to the bowling alley/arcade/laserquest. There are a couple of shopping centres in Woking and it's all pedestrianised, but it's basically a modern High Street.
If you want to visit the Common, it's somewhat distant.
Here's a map of the town centre:
www.streetmap.co.uk/map.srf?X=500565&Y=158973&A=Y&Z=115
Martian is just to the right of the arrow.
If you move the map to the North, there's Horsell village, and then the most popular bits of Horsell Common are above that.
If you look at the Horsell Common Preservation Society's website, there are a couple of walks at
www.horsellcommon.co.uk/find_a_walk.php
The 'easy' walk goes from the car park next to the Six Cross Roads roundabout via the sandpit. I think the sandpit has some kind of War of the Worlds connection.
If you want a longer route from there, referring to the streetmap above, you can walk up past the farm marked as 'Anthonys' in the top right, and then through the McLaren Technology Centre grounds, which are pleasant enough with some landscaping. Various of the McLaren F1 cars are visible through the windows. Continuing up from there you can go across the side of the runway at Fairoaks airport, which is basically for rich men to fly their small planes, and then at the Chertsey Road, either cross and go up the track towards Stanner's Hill, where you'll meet a path, or for a shorter walk just walk along the verge on the side of the Chertsey Road (which as traffic).
Then return along the track back on the opposite side of Fairoaks Airport from whence you came, which leads back across fields onto Horsell Common from where you can walk back to the car park.
If you want to start from the town centre, but see some of Horsell Common, then the best approach is to walk along the canal, which is just across the A320 (pelican crossing), passing a playground along the way.
If you carry on along the canal you'll reach Monument Road, cross this road, and there is a car park. Just next to the car park is a Bronze Age barrow, in a very good state of preservation, and a few yards through the woods (Horsell Common) is Britain's first Muslim burial ground, built in WW1 to house Muslim soldiers, but now empty of its graves.
On the other side of the road is another barrow (marked on the map 'tumulus'), and you can walk through Horsell Common emerging at Wheatsheaf Common (the white rectangle to the right of the A3046 and left of the green woods on the map), which is a recreation ground with a playground.
The Southern part of the Common is much less trodden than the Northern, although it is closer to the town centre, the thing is the Northern bit has more open heathland which is more inviting than woods, and also it is bisected by two busy roads. It is however closer to the town centre.