There are many things in Monster Life that you're not supposed to do, but here are some tips on optional features and what you probably shouldn't do.
Don't show distrust to the "weak" monsters
Don't overuse strong monsters. If you are impatient, you can use your weakest monsters (Diggster, Domoster, Mothster etc.) and try to win battles with them while your strongest monsters are recovering for 16 hours.
Don't just rely on element strengths
You would think a Pumpkinster would be useless in front of a Pegaster, right? Try it! Taking chances and risks increase your knowledge about the game. You might find that Pumpkinsters could be great against Pegasters!
Don't buy the silver or gold lottery unless you are willing to buy Crystals
The silver and gold lottery cost a lot of crystals. Even though they give better prizes, crystals are very hard to earn, so don't waste them on the silver or gold lottery.
Don't buy the gym
Don't waste your crystals on decorations
You might notice in the booster section of the shop, there are decorations that cost crystals. Even though they are listed as boosters, they do not give any sort of boost. Don't waste your crystals on these unless you have so many crystals that you don't know what to do with them.
Don't overlook Vaccumster, Diplodoster, Stonester, Rhinoster, Snailster, or Boarster
If you are facing one of these six, you might be thinking; These monsters are very slow. Even though they're powerful, they'll never hit my [insert speed 3 monster here]! Think again! Normally, Speed 3 monsters are not very powerful, but the above mentioned monsters have high health at level 3 (excluding Vaccumster), and the Speed 3 monsters normally have low health at level 3. This means that even though the Speed 3 monsters are very fast and hit more often, they don't have as much firepower, and the Speed 1 monsters will hit eventually, and they will hit hard. Again, since the Speed 3 monsters tend to have low health, the speed 3 monsters will be knocked out in a few hits.
Don't battle when unprepared
Face it, we don't want to wait for the monsters to recover for 18 hours, but you might be thinking, "I'll just go battle those dragsters." Miracles probably won't happen! If you use weak monsters, they'll get defeated and just need more time to heal. Be patient, unless you want to waste your Tamanos.
Don't overlook your monsters
You might think "Oh, my monsters are the worst!" if you only have Diggster, Hornster, and Domoster. But if you keep on trying, level them up, and energize them, you will find they can be powerful! Remember, you do not need to use these monsters the whole game. Eventually, you will get better monsters, but make sure to still show some love for your veteran monsters!
Don't buy the monsters who's prices go down on holidays
Say, you brought Pilgrimster which normally costs 360 crystals, but on Thanksgiving, it costs 36! You just wasted your money, but feel free to buy them anytime if you buy crystals, or need more monsters badly.
Don't overlook the fast monsters with weak firepower
You know Crabster has a speed of 3. It's attack range is 6-9. You might be thinking:"6-9? Useless!" But wait, those monsters can be used in the early battles if you want to redo them. Also, you probably will have an advantage over the weak monsters in the early levels. You can also use them on the Training Grounds.