Warn players that their turn is coming up by saying " Tom its your turn, Brian you are next". It cuts down on the time spent thinking.
This really helps at my table.

Roll multiple dice together, and color code them.

If someone dont know the rules for what they are trying, they cant do it. They have the entire round to check rules, their turn is for acting not for books. It shouldn't be set in stone, but be a general rule.