Here i will give you some tyranid tactics to use in your battles, by examinig the different troop types.
The tyranid army list is large and very diversified, but is not as flexible as you cna think. They have a basically straightforward attack type, which is rip out their enemies guts in HTH combat. The best way to do this is to screen all your troops with pleanty of termagants. Follow up with a wave of hormagaunts to kill any small and weak troops. Genestealers and tyranid warriors (armed with close combat weapons) come next, and will rarely be harmed by enemy fire because of the termagant skirmish screen,.
The best way to support your swarms is to use broods of tyranid warrors with long ranged weapons to try and pin down enemy troops who will shoot your army to pieces. This is where bioveres come in as well. They can fire over intervening terrain which puts them at a huge advantage.
The hive tyrant can be tailored to either assault or heavy weaopppn roles but they can't do both at the same time. If you go for assault give them devourer with a bonesword and spinefist. If you go for a heavy weapon warrior go for a venom caannon and whatever else you like. The only psychic powers worth buying are psychic scream and catalyst. They are the most useful out of any of the psychic powers available.
Gargoyles deserve special mention along with lictors, as they are superb at destroying enemy heavy weapons through flying high and infiltration. Lictors are also superb at taking outenemy characters and delaying a part of your enemies force. Carnifexes will be mentioned here as well, as they should be placed in the middle of your assault swarm and used as a mobile bastion of power. give them a voltage field and/or regeneration and you should be able to withstand almost everything that the enemy can throw at you during the game.
Tyrandi armes ahave a few options when choosing their route of advance. You should of course advance through the place where you can move the fastest toward the enemy,but you shouuld also take into account any knind of terrain to block lines of sight from your enemies heavy weapons. Moving up the flank is usually the best way to do this while your gargoyles and lictors delay the enemies opposite flank and center.
Thanks for staying with my ramblings till the bitter end and i hope these tactics help you in your battles. Aloha!