This is a small map, part of the original maps released with the game. You start with one Orb and three Power Wells, and there are six Monuments and twelve Wells available for expansion.
Wazhai has many cliffs and obstacles, and as always this means Towers and Flying creatures are especially good here. But its most unique trait is that you start with three wells instead of the usual two, which makes for more aggressive and fast paced games. Many players fail to adjust to the rhythm of this map, and for example tech too slowly. The third Era often comes two or three minutes sooner than usual, and this takes some people by surprise.
The logical choice for expansion are the bases horizontally aligned with your starting position. Meaning the north east base if you spawn north, or the south west base if you spawned south. This is because of the cliffs. If you take the south expansion while being north, your enemy can easily send long ranged units from his original base to the cliff over your expansion and keep pressure on it from there, possibly with the help of towers. Also the walls between those expansions and the enemy base are closer to your orb/well, meaning that they are also vulnerable to long range siege and mortar towers from there.
However if you feel comfortable defending the inverse positions (the ones vertically placed in relation to your starting base), it might be a good idea to take them if only to secure the Monument on the side for your T3. (That orb would be placed between your starting base and your T2 expansion, which means easily defensible. But some people also take those inverse positions because they want to have access to the enemy base from the cliffs from a short distance. So taking the vertical base or the inverse all depends on what you are planning to do. (Horizontal is a better defensive position, while the inverse gives better offense openings.)
For wells, an interesting position is the one with 2 wells above your base if you spawned north, or the 2 wells bellow you if you spawned south. This is because they are far away from your opponent reach, and are rarely attacked because of that. However you must make a big detour to capture those positions yourself, which might cause a problem if your opponent does something that requires a quick reaction from your starting unit, like a tower or T1 rush. (This is why it is recommended to capture these only later on in the game.)
The second choice for expansion are the Monuments exactly west and east (at 3 and 9 o'clock) in the map, close to the map borders. There you will find a single Monument, that is vulnerable to long range siege and towers, but that is rarely attacked because it is hard to reach and far from your opponent base (if you build the one closest to you, and if your opponent didn't expand nearby).
The least interesting choice are the middle Monuments and wells, because they are too vulnerable to towers built on nearby cliffs, and to flying creatures that would be at a very short distance from opponent base to them. However if you are playing very aggressively and keeping the pressure on your opponent (maybe with ranged/flying/towers of your own), those bases can make for excellent expansion points.
The most common strategy is to try to tower rush the opponent by making towers on the cliff directly above his two starting wells. Most successful rushes are done with Mortar Tower, or Cannon Tower at T2. But this strategy also works with ranged units, especially Windweavers at T1. If You Try To Do This You Will Lose The Game Against With Anyone With A Brain.
Map control : north east position and south west positions give a clear advantage, since they dominate the close by center positions. This is mainly because center positions are very vulnerable to towers built on the cliffs directly above them at 45 degree angle. Mortar Towers and Termite Hills, but also Cannon Towers work very nicely there and can easily take down the well or orb built there. This is why the positions at corners are very popular, they let you put pressure on center positions very easily. Especially if you can capture both corners.
Bigger, more expensive creatures (Mountaineer, Harvester) are more viable in this map because of the increased starting wells count. Not only you can summon them sooner, but more energy will be available for supporting them with spells.
Using Flying creatures as mentioned previously. The cliffs provide for an easy harass, and you can switch between your opponent's main base and expansion easily, since the map is small and you can travel very fast from one point to another.
Map control. Positioning is very important, and each position taken by your opponent will make openings in his defense. You have to exploit this, and be on the lookout for a T3 orb since as said previously, T3 comes early in this map.
But most importantly it is capital to be aware of when you can tech to T3, and when your opponent will be able to also so you can either tech or destroy your opponent orbs on time.
A lot of wells and orbs are accessible from cliffs to ranged T3 creatures, which means you generally see more ranged T3 than melee here. The center positions are a primary target, but also the orbs at 3 and 9 o'clock, since you can reach them from over the cliffs with most ranged T3. (And some ranged T2 like Mountaineer.)
You also see a lot more flying units in this map (Swamp Drakes, Magma Spores, etc) for the same reason you see flying at T2; the many cliffs and obstacles combined with the small size of the map make hit and run attacks very powerful and hard to counter.