If you have the crib and are not sure what to put in it, throw in a pair or "high" 15 (e.g. 9 and 6, or 8 and 7). All things equal, it is better to have lower number cards in your hand during game play to effectively allow you to earn more "last card" points. This also ensures you keep the scoring set of two cards together (because it is your crib).

During gameplay points are also scored for pairs, sets of 3 or 4, runs of 3 or 4, or when the total adds up to 15 or 31. Because of this, it's important to think ahead to what your opponent might play. For example leading with a 5 is often a bad idea since 10s are the most common card value and your opponent bringing the count to 15 will net them 2 points. Similarly, ending your turn with the point value on 21 is also not ideal since it's likely your opponent will have a 10 and bring the count to 31 for 2.

Consider going to the hamburger menu in the upper right corner and selecting Auto Go and Auto Cut to speed things up.