Away fans are located at one end of the ground in the North Stand (usually in the upper tier only). Around 4,000 away fans can be accommodated in this end. Like the general improvement in football, a trip to Millwall is not as threatening as it once was. However, it is hardly a relaxing day out and I found the Den to be quite intimidating. The large police presence at the match I attended did nothing to dampen this feeling. I would advise that you exercise caution around the ground and not to wear club colours.
If travelling by train then it is probably best to grab a beer around London Bridge before moving onto the ground. I would advise keeping any colours covered, even when drinking in the London Bridge area.
... best to go by rail, as South Bermondsey Railway Station is only a few minutes walk from the ground. There is a direct walkway specifically built for away fans which takes you directly to the away end and back to the station afterwards. This has made the Police's job of keeping rival supporters apart so much more manageable. As you exit the station turn right for the visiting supporters walkway.
.... the Police are well drilled in getting away fans into the ground from the special train and safely away afterwards. Although don't be surprised if you are held in the stadium for sometime after the final whistle, before being allowed back up the walkway to the station. You may also then be held for a while at the station itself, so please bear this in mind when booking the time of your return journey home.