I've played a few games of Azul now, predominantly 2-player on the grey side. A lot of players restrict the score they can get by forcing their placements into the same diagonally-striped pattern as on the coloured side. If you do this, you likely score fewer points because you're probably not placing optimally, i.e. next to existing tiles.
I tried to think why players would do this, and then I thought that maybe there is some difficulty in working out the Sudoku-like rules for tile placement, and players block themselves in the late game and end up throwing points away on misplayed tiles.
One shortcut to not block yourself in late game is to recognise that if every column and row must only have each colour once, then every 3x3 square must have at least one of every colour. If you're thinking of placing a tile which would break this, then think again! (You might want to do it on the last round though).
TLDR: don't play diagonal patterns on the grey side.
I tried to think why players would do this, and then I thought that maybe there is some difficulty in working out the Sudoku-like rules for tile placement, and players block themselves in the late game and end up throwing points away on misplayed tiles.
One shortcut to not block yourself in late game is to recognise that if every column and row must only have each colour once, then every 3x3 square must have at least one of every colour. If you're thinking of placing a tile which would break this, then think again! (You might want to do it on the last round though).
TLDR: don't play diagonal patterns on the grey side.