Man Utd

Getting to the ground
You can catch a tram from the city centre to the ground. It takes around 10 minutes from Piccadilly Gardens. Note that St Peters is better than Piccadilly Gardens because it's a more frequent service, every 3 minutes as opposed to every 6 minutes (6 and 12 minutes on Sundays). It's also the most convenient stop for the Waterhouse or City Arms. You get off at Old Trafford, Pomona or the recently opened Wharfside depending on which service you catch. Basically, follow everyone else for getting off and walking to the ground. It's about a 10 minute walk from Old Trafford, 3 or 4 minutes more from Pomona, Exchange Quay is better than Pomona after the game because trams stop there first. A taxi, if you can find one, is a relatively quick and cheap way of getting to the ground. Note that the special train service from Piccadilly to Manchester United Football Ground station no longer operates. Neither do the special buses. There can be horrendous queues for the trams after the game, and it can be quicker to walk the whole way back to the centre, all three miles of it. A One Day Travelcard for the trams is 3.50. However, it's best to use Contactless. Just tap on and tap off, and you'll be charged the minimum fare for the journeys you make. There's full info on it here.
 
If you decide to drive over then I haven't any first hand experience of parking. There is though street parking available within a 10-15 minute walk of the ground, including in the area around the Quadrant (see Pubs below), provided you get there reasonably early. Alternatively, you can park at the Lowry Mall at Salford Quays. This costs 4 for four hours, and the access from/to the M602 is very good. The Lowry Mall is marked on the pub map.   

Pubs
All the pubs around the ground are basically home fans only. There is though one place near Old Trafford tram stop, the Quadrant, which allegedly gets a mixture of home and away fans. Not only that, there are a few takeaways very nearby, not to mention an offy in case service in the pub is really bad. The bars in Salford Quays, including the Lime Bar, are also apparently ok for away fans, as is the Matchstick Man, a Hungry Horse outlet.  Another option is Sale town centre, which is only 8 minutes away by tram (from Old Trafford stop).

For train travellers, your best bet is to drink  in the centre and then head to the ground late on. If arriving at Piccadilly, I would recommend the Bulls Head, a proper traditional pub with seven cask ales and cheap pub food. Not far from Victoria, and really handy for the Shudehill tram stop, are the Hare & Hounds and the recently refurbished and re-opened Lower Turks Head. Both are also proper pubs. There's a Spoons, the Seven Stars, close by. Another city centre pub worth checking out is the Unicorn, which isn't far from the Market Street tram stop. In the area around the St Peter's Square tram stop are a couple of Wetherspoons, the Paramount and the Waterhouse. The latter is smarter than your typical Spoons, with prices to match. You can do better though in the nearby Vine and.City Arms, which is a belting pub with eight real ales on at any one time. Both open at 12, and the Vine does food. Not far away, the Grey Horse is tiny but an absolute gem! 
 
 
Pub map
City centre pub map
Football Ground Guide
Metrolink