Getting to the ground
The ground is a 20 minute walk from the stations. There are two - Wallgate for Manchester trains and North Western for (mainly) Preston trains. It's also 20 minutes from the town centre if you take the shortest route (see pub map below). As if that wasn't bad enough, the away fans are housed in the North Stand, which is the furthest from the stations/town. An alternative to walking is to catch the bus - the 628 runs from the stations to the Red Robin pub every 10 minutes on Saturdays. Unfortunately there's only one an hour on Sundays though.

If you're driving over then it's M62/M60/M61, leaving the M61 at junction 6. There's parking at the ground, but it'll cost you and in any case it'll probably take you ages to get out afterwards. You're much better off parking on the other side of the canal from the ground. There's quite a bit of street parking on and around Woodhouse Lane, and it's really good for a quick getaway after the game.
There are very few options around the ground. Particularly handy for away fans though is the Marquee, actually built into the stand under the away section. Then there's the Red Robin, which is a family pub. And that's it. The nearest proper pub is the Brickmakers Arms, which is a 10 minute walk away over on the other side of the canal. This is actually the best bet for anyone driving over as there's plenty of street parking in the area and it's good for getting away after the game. The Brickmakers is a lovely traditional boozer. It gets very busy towards kick-off, but that's to be expected. There are a few other pubs in the same area, but none of them are anything like as good.

For those arriving by train, the Swan and Railway, directly over the road from North Western station, used to be home fans only, although I'm not sure if that's still the same. There are better options anyway. My two recommendations are the Anvil and Wigan Central. These both have an extensive range of beers available and get consistently good reviews. I can personally vouch for the Anvil, which has the advantage of being sort of on the way to the ground. The Berkeley also has a decent selection of beer and gets decent reviews. And of course there's a Wetherspoons outlet, the Moon Under Water.

All the above pubs are marked on the pub map below.
Pub map
Football Ground Guide