the first weapon that you receive (this) is one of the best, if full upgrade can kill most zombi with one hit in the head, the best one however, is the knife, if you learn to use it, you dont need any other weapon. flash granades can kill all those crows, and those disgusting thing that appear after the head of some zombies is destroyed. when fighting against Krauser, use the knife. well, there is more than five years since I last played.
Upgrade gun capacity when it's empty, free bullets. Check out which jewellery combines for more cash.
Try to always shoot them in the head and then run towards the one you shot and kick him, it saves a lot of bullets and hits other "people" around. If there are no more zombies close, you can stab a downed enemy to death. Sometimes is a good strategy climbing towers or something like that and hiting with the knife when the fake zombies are climbing the stairs and have their head over the edge. Also, dont sell right away all treasures that you encounter. Some of them have multiple parts that, combined, sell for much more money. I guess this are the more important and basic tips I can give you...
Keep an eye out everywhere for crows, if you see any kill em before they fly they usually drop good stuff like grenades, money and herbs. Ignore whomever told you to upgrade your first gun, upgrade the punisher which you get from the graveyard challenge, upgrade that one its better. Always get the case upgrades first over everything else. When near water keep an eye out for fish and shot em if you see em they are similar to crows. Save the dog on the start, it helps later on in a boss fight. Save your herbs for combination so that you can upgrade your hp bar as soon as u get one of each color.
it's fun. you get to buy an infinite rocket launcher, and you can just blow stuff up. even bosses would die with a shot, so much fun.
ALWAYS expand the suitcase if you can. ALWAYS maintain it organized, so you never waste space and know where everything is. Complete the target shooting practices sessions (there are 3 I think). You get money and collectibles, plus you sharpen your skills. And NEVER forget that annoying brat Ashley. Use knife in animals and boxes, don't waste ammo. If you stab someone's knee he might fall and you can do a special attack on him ammo free. Keep an eye out for treasures but don't sell them immediately, some of them can be combined into a more valuable one. Tha's about it.
Huh? I've hardly ever find myself without ammo during the whole game.. almost empty, yes, but not totally empty...