Okay so comparing Pokemon Duel to checkers isn't 100% spot on, because there's definitely more to it than that, but it's still fairly apt. The game has you moving your statuettes in an attempt to land on your opponent's goal while defending your own, with different minis each having their own movement speed and attacks. Trust me, it's a little like chess or checkers.
First, you're going to want to get your team set up.
Pay attention to each pokemons' attack ring. This ring, viewable on their individual data pages, will give you an idea of how likely an attack is to activate – the bigger the slice the more likely.
Red is bad. Red bits are for misses, and missing leaves your pokemon vulnerable to even the weakest attack. So maybe consider not using ones with big red areas.
'Speed' is also important. The number inside a blue circle, which is underneath the pokemon's statue, shows how many spaces that pokemon can move in one turn. More spaces means more opportunities to block, close in on, and otherwise best your opponent.
Don't forget about Plates. Plates are a bonus you can activate once per match each (don't worry, they'll be back for the next one). These can be used to temporarily increase a pokemon's attack, give you a second chance spin in battle, swap places with other pokemon on the field, and more.
Fusion ever so slightly increases a pokemon's effectiveness. Rather than increase their stats, it will make one of their ability 'slices' of your choosing on the wheel a little bigger (and their miss sections a little smaller) – thus making the chosen attack more likely to occur.
Hop to it
Most of the time, winning a match is more about positioning than direct battles.
Watch the corners. Each of the four corners on the field is a spot for pokemon to be placed – the two on the top for your opponent and the two on the bottom for you. Placing a pokemon on one of these spaces will render it useless, which means you can prevent your opponent from placing more but the same can happen to you if you're not careful.
Quests (the single player mode) and Training are where you'll want to practice before taking on other players. They're also a relatively easy way to earn some extra items and other goodies.
Go for the goal. Knock-outs are only temporary setbacks – the best way to win is to get one of your pokemon into the opposing goal.
Use the board layout to your advantage. If you move your pieces strategically you can make it much tougher for your opponent to reach your goal or even defend their own. Even weak pokemon can make a good wall.
Don't sweat the battles. Unless you use a specific Plate ability, you have zero input during a fight. Just sit back, cross your fingers, and see how it turns out.
It's a bit offbeat, but Pokemon Duel actually ends up being pretty enjoyable. It's mechanically simple but like other much older classic games there's a lot of nuance to the strategy. Not a bad time at all!