The Baal Predator is an anti infantry tank which can be use in the Blood Angel army on the Fast Attack slot. A brief version of the fluff is that apparently Blood Angel techmarine found the Baal Predator STC(Standard Template Construct).. and apparently they decide to be complete assholes and not share it to the Adeptus Mechanicus. Also the Baal Predator comes with the special Lucifer pattern engines which makes their tanks Fast. Which our poor Ultramarines and their chapter equivalents denied from this goodness of goodness.
So down the fluff and now with the tactics... Generally The Baal Predator has the same stats as a normal Space Marine Predator. Now it 5th ed they are given the special rule scout, this is a huge advantage as Baal Predator is a mid range - close range tank so scout grants them this ability to either flat out on their scout move or outflank. This helps them to get closer to the enemy earlier on.
The have the option of eitier using a Twin-linked Assault Cannon or the Flamestorm Cannon which both are equally devastating on their on right. You can add either heavy bolters or heavy flamer sponsons. You are free to tinker whatever combination feels right for your army but here a few combination i usually go for.
Twin-linked Assault Cannon turret with heavy bolter sponsons and pintle mounted Storm Bolter
The idea of this combination is actually to maximize the amount of shots you can dish out to Hordes in the open and even MEQ. You already getting 4 from the Assault Cannon + 6 from Heavy Bolter and 2 from storm bolter. That a total of 12 shots which 4 are twin-linked. It equivalent is the Predator Destructor which is cheaper than the Baal doing 2 autocannon + 6 heavy bolter and 2 storm bolter shots.. however the problem is you run the risk of missing alot unlike the Baal which has a twin-linked Assault Cannon which guarantee you 3-4 shots. Also it comes with rending so you can tear heavy armor or elite infantry which is rare but atleast u got a shot for it.
Flamestorm Cannon turret with Dozerblade.
This one is a more aggressive Baal Predator as it job is to storm into enemy infantry position and burn them with the S6 Ap3 flamer. You also have the option to eitier use the scout movement to quickly rush to a location or outflank to flush the enemy position. Dozer blade is important as most of the time you be taking out infantry well inside cover so you are gonna go though alot of dangerous test. As the last thing you want is to get immobilize in front a swarm of orks. You may add heavy flamer sponson if you like but in my opinion it difficult or rare to actually use the sponson as you be moving 12" all the time and you rarely get the chance to move 6 and use the sponson. Another thing u can add is a pintle mounted Storm Bolter which just add a bit of shots for each time u burn.
One key weakness when using Baal Predator is the weak side armor especially since Baal Predator is a mid to close range tank. It easy for your enemy to flank them and take them out. So you may want to eitier take advantage of terrain or have it side guarded by other less powerful tank/units.