Keeping a close eye on your opponents is one strategy that works. You can learn a lot about their possible hands by keeping an eye on the cards therummy all app list 51 bonusy draw and discard. Making strategic choices about which cards to keep & which to discard can be aided by this information. For instance, it might be a sign that your opponent is aiming for a particular meld if they routinely remove cards from the discard pile that you have already discarded.
rummy all app list 51 bonus