How to load assets or wait for character to load ?

Hi I've scripted a heavy game but the problem is when joining scripts are inconsistent, I'm using this code but I feel it's not loading assets or the player is loaded when this fires, therefore making the code not work.

For example I have a script that changes your shirt when you join but it doesn't work all the time.

Any help would be greatly appreciated.

Players.PlayerAdded:Connect(function(player)
    player.CharacterAdded:Connect(function(char)

end)
end)