HOW TO... STOCK UP ON MORE ITEMS
Watch out for breakable crates, which are often found in side rooms, and smash open as many of them as possible as they contain ammo, grenades, herbs and skill points. Also look for special crates that can be examined and opened when approached, as these contain items that provide large skill point boosts.
Make sure you pick up any items dropped by enemies or from smashed crates as soon as possible, as they disappear after around 90 seconds. This may sound a long time, but if they appear in the middle of a firefight you could easily miss out if you don't grab them quickly.
Regularly manage your inventory to make sure you're not carrying any unnecessary items and keep at least one slot free so you can grab a herb in a pinch. Bear in mind though that any items you discard from your inventory are immediately lost and cannot be recovered, so choose wisely.
HOW TO... DEFEAT THE TOUGHEST ENEMIES
As well as the standard zombies and J'avo there are a number of tougher enemies that appear from time to time, and knowing the best approach for them will help you take them down quickly.
Shriekers are zombies with inflatable neck sacks, and if they're allowed to scream the sound will summon more enemies from the surrounding area. Shoot them repeatedly to halt them in their tracks, then blast their neck sack as it's inflating. This will defeat them and also send out a shockwave that kills any nearby zombies.
Whoppers are the huge fat zombies that lumber towards you and can deal large amounts of damage. To take them down, first aim for their legs and shoot until they turn red. With both legs done they will collapse, and you can then aim for the head to finish them off.
Noga-Let (winged creatures) and Noga-Trchanje (spider creatures) are both mutated from J'avo, who you can still see attached as part of them. Aim for the head of the consumed J'avo as this is the weak point for both of these enemy types.
You will encounter a number of BOWs, which are particularly susceptible to flash grenades. Use these to stun them (taking care not to blind yourself in the process) then follow up with additional attacks while they're vunerable.
HOW TO... USE YOUR PARTNER MORE EFFECTIVELY
If you're playing with an AI partner, then holding down B/Circle will locate them for you and bring up a list of squad commands. You can use these to direct your partner around, and pushing Up on the D-pad will instruct them to attack the enemy in front of you.
Squad commands can also be used to target specific enemies, by aiming your laser sight at them then hitting B/Circle to set a target marker over their head. Your partner will then concentrate their attacks on that enemy, which is very useful when facing tougher foes and bosses.
If you partner is downed, you can simply revive them with no extra health by approaching them and pressing B/Circle. If you want to boost their health as well then instead press RB/R1 one or more times corresponding to the amount of health tablets you want to give them from your supply.