Tali is a sort of poker with dice and less money. You roll five dice three times and try to create the best hand. Your two re-rolls may include any or all of your dice.
The 63 points needed for the bonus in the upper half corresponds to getting three of each die type in each row. If you score more than three dice in the fives and sixes rows then you can afford to place a bad roll in either the ones row or the twos row and still get the bonus. In the Colors version, you get a bonus of 55 if your upper half total is between 71 and 77, and a bonus of 75 if your upper half total is greater than 77.
Don't forget about multiple yahtzees, if you roll a second yahtzee you can also put it in the yahtzee row for even more points. This only applies to the regular game.
When play starts, you see the results of your first throw of the dice.
You can only use each combination once, i.e. once you've entered something in a slot, you can't change the score later if you roll a better hand.
There is one exception to this rule, if you roll a yahtzee a second time you can put it in the yahtzee row again for an extra fifty points. You can keep doing this each time you get another yahtzee. At the end of the game you will be given extra rolls to fill in the other rows. Be warned that if you score zero in your yahtzee row (i.e. you filled that row with something that wasn't a yahtzee) then you can't put a yahtzee in afterward, zero is all you will score.