The first? Your eardrums will be melted by blasts of the Stereophonics over the stadium PA system. The second is that you will get no favours from the referee.
And so it turned out at the Parc y Scarlets on Saturday. Music lovers might have been relieved to hear only the occasional contribution from the Welsh rockers, but watching Italian official Giuseppe Vivarini at work was an altogether more frustrating experience for the heroic handful of Glasgow fans (including a couple of eardrum melters of their own) who made their way to the game.
Like most sides nowadays, Scarlets work hard on their defensive line speed. And, like all sides, they might occasionally steal an inch or two in their anxiety to get at opposition ball. On Saturday, however, that larceny could be measured in yards - a crooked alignment in every sense of the word - but Vivarini appeared oblivious to their offences. Meanwhile, the touch judges' take on the matter might have been better indicated had they been wielding white sticks rather than flags.
As a consequence, the pressure on Duncan Weir, making his return at fly-half after a six-month injury absence, was immense. The 22-year-old had lost none of his characteristic cool while working his way back, and he marshalled Glasgow's effort quite brilliantly. Weir is a rugby pragmatist at heart, and his decision making throughout was faultless.
"It was good being involved in the matchday experience again and great to come away with the win," he said. "I felt I was getting the ball through my hands pretty well. That was my key - to keep it simple, not try to do too much in my first game back. It ended up being a smooth ride."
Well, up to a point. Glasgow may have controlled the scoreboard throughout, but were put on the rack in the third quarter as the Scarlets, who had trailed 14-3 after 30 minutes, pegged back Glasgow in their own half and cut the deficit to two points.
The expectation among the home supporters was palpable at that point, but not for nothing have Glasgow kept their try-line intact in four of their five PRO12 outings this season. Granted, Scarlets did not help their own cause with a couple of attacks of white line fever when scores seemed to be looming, but Glasgow's refusal to buckle turned back the tide in favour of Gregor Townsend's side.
Townsend has every right to be proud of Glasgow's 100% winning record and their position at the top of the PRO12 table. But he conceded there is huge scope for improvement. In short, they look far better on paper than they have on grass, but winning ugly is still a far better experience than losing prettily.
"It's hard to say what playing our best is," said Townsend. "We played our best last season in the semi-final [against Leinster] and we lost. We're playing well enough to win games."
Well, the games they have played until now at least. Next weekend, when they travel to France to meet Heineken Cup champions Toulon, will be an altogether different kettle of poisson, and a huge step up from the standards of the past few weeks.
With his performance in Wales, Weir may well have nailed down his place in the side that lines up in the Stade Mayol on Sunday. That said, there has been some crafty psychology behind Townsend's use of 36 players over the course of five competitive games to date, and the coach now has a group of players who are all itching for European action.
"The strength in depth is great," said Weir. "Guys keep filling the jersey and putting in the performances. There will be a few disappointed because everyone has been holding their hands up for selection. Toulon are champions, which says it all. It's a fierce environment to go and play, but we're looking to keep this good run going. I don't think any other Glasgow team has won five in a row at the start of the league."
Glasgow set themselves up for that with a glorious, rampaging start. By the time Ryan Grant was thrust over from a ruck for the opening try, after three minutes, only one Scarlets hand had touched the ball - and that to knock it on and give Glasgow a scrum. In retrospect, it was something of a surprise that Glasgow managed to resecure at the set piece, for they toiled in that department all evening. Captain Al Kellock was clearly furious about some aspects of the Scarlets' technique, but from the sidelines it looked as if Glasgow were being beaten fair and square, not that either of those terms is particularly pertinent at scrum time.
Glasgow's second try, in the 30th minute, was a smash-and-grab affair, a thrust down the right touchline by Mark Bennett preceding a switch to the left, a series of rucks on the line, and a touchdown by Tim Swinson.
"We've won but it doesn't mean we are the finished article," added Weir. "We need to work on a lot of areas. It's about tidying them up every week, making sure they don't continue. We need to cut out problems at source."