The overall objective to win the game is to score victory points.
the Eldar player scores points depending on how many tyranid forces have come into play, while the Tyranid player scores points by devastating areas of the craftworld and killing certain units.
The Eldar player has slightly the easy side as his victory points are automatic, so the game evolves around denying victory points to the Tyranid player.
The Eldar assets;
Elite ground forces; they have a few ground troops that are both very strong and dont count for stacking, these are a big plus for ground combats and keeping these alive is important, coupled with some great leader counters
Area special abilities; they range from reinforcements to shooting tyranid ships out of the sky and inspecting their stacks.
the reinforcements are the top priority ones, helping you to replace any losses, shooting at the tyranid ships is important to decrease the tyranid stacks to an acceptable level for space combat.
spaceship mobility is the last Eldar asset, in fact, managing your fleet is essential to winning the game.
Your strategy should be focused on destroying the tyranid ships while in space to prevent them from landing troops on the craftworld.
while the Eldar ships might seem weak with combat factors 4/6/8 in regards to the tyranids combat factor 10, but your mobility allows you to concentrate your ships easily and pick out the target's of choice, also, as the Eldar ships fire first, you can take on a potentially stronger stack of Tyranid ships. it is important to save your ships and thus only attack weaker stacks, avoiding bigger stacks until the barrages dwindle these stacks to a more manageable level.
You want to keep as much ships in space and your means to do so are the reinforcements; you can convert guardian ground troops to ships and as these can be replaced as well, you shouldnt be running out of ships too quickly. the remaining Eldar ground forces are generally sufficient to beat any Tyranid ground attacks.
as the 6/8 factor ships are not replaceable, you really want to avoid losing them, always keep 4 factor ships as cannon fodder and retreat if none are available.
at moments, it may look like there's too many Tyranid ships to fight them all so you should be picking your targets.
you could/should allow lone tyranid ships pass to land on the craftworld as on their own, they should be easy pickings for your ground troops.
Dont be tempted to spread out your ships and remember that, as you cantpredict the entry point of the following tyraznid reinforcements, that staying in the outermost spaces might be very risky.
Try to split up the tyranid forces as they are strong in numbers only.
an important source of reinforcements are yriel's raiders, you might want to intentionally let the tyranid player attack Yriel's shrine on the craftworld to receive these, in fact I dont bother defending this area.
these added ships really increase your space combat potential.
If you see that space combat is no longer viable due to too few ships, then you should convert to ground troops and concentrate there.
you really want to limit the ground combats to a minimum as this is where the tyranid player can harm you the most and the only choice he has to gain victory points. retreat from devastated areas to maximize defense in the others and use your free stacking units/leaders to maximize counterattacks.
The Tyranid assets:
combat factor of 10 in space combat and seemingly unlimited reinforcements.
As the Tyranid reinforcements are very random, both in quantity and location of entrance on the board, it will be challenging to concentrate your attacks.
You should focus on moving your ships into big stacks, dont hesitate to move sideways to achieve this. only these big stacks will enable you to defeat the Eldar ships in space combat. avoid 1-1 attacks as the Eldar first fire ability makes such attacks too costly.
at the start of the game you must concentrate on eliminating the eldar spaceships. the quicker they're gone, the more easy your troops can land on the craftworld later on. if you can choose between landing or fighting in space, choose the latter, you only want to land if you have sufficient units to attack together, although dont pass out a chance to take out important areas, you really want to limit Eldar reinforcements and barrages.
Try to avoid attacking Yriel's shrine, you should only do so later in the game, close to the end to maximize your points.
If at some point, your reinforcements run dry due to a double roll, you should immediately concentrate solely on ground combats to reek in a maximum of victory points before you run out of troops.
Dont despair if you have bad luck with the rolls as this game is quick and you easily restart and get several plays in an evening.