Here are some useful tips for beginners of Horizon Zero Dawn.

Use Your Auto/QuickSaves

Be aware the game preserves the last 10 auto/quicksaves. If you encounter a bug or regret a decision, make use of them.

Unique Bows And Slings

Also be aware that there are multiple bows and slings, each with their own unique ammo types.

Optimal Weapons

Every weapon is optimal in some situation, no weapons are always optimal.

Increasing Storage Capacity

Check the crafting menu to know what to be in the hunt for to increase your storage capacity.

Practice Makes Perfect

Hunt down machines & just grind out kills. It's great Exp & the practice in invaluable. Learning how to use stealth, dodge attacks, plan your approach, fight up front or from a distance, & how each machine behaves in incredibly important.

Use Focus To Scan

Use your Focus to scan enemies for strengths, weaknesses, and specific weak points.

Farming

Shoot and loot a bunch of wildlife. You can use the meat to craft potions, and the skins and bones to craft larger pouches for ammo, resources, etc.

Take Your Time

When you come up on a camp of human enemies, use your focus and mark them all. Then work your way around, kill the ones on the outer perimeter and work your way in. You can also try guns blazing, but even humans will take you down in numbers. The AI is pretty bad if you're stealth killing, but if they attack in numbers...

As for machines, especially the bigger ones, look around at your environment. High ground is ALWAYS good. Call it a cheap tactic, I call it using an enemy's weakness to my advantage.

When you finally go west watch the skies. There's something BIG flying by the main road, if you're on it. If you don't actively avoid it, it WILL see you and it will most likely be outgunning you at that point in the game.

Best Use Of MultiShot Arrow Perk

The best use of the multishot arrow perk is for the elemental arrows, not so much as a damage multiplier. Three freeze arrows will usually be enough for 100% freeze status effect, etc.

Whistle Perk

The perk that allows you to whistle for a mount any time is more useful than you would think.

Mounts Can Help Clear Enemies

I once rode in on a fort, got off, cleared one side of the entrance, then when I went to the other side, my mount had killed all the enemies himself.

Thanks to EruditeAF, popnlocke TheNineteenthDoctor and others for submitting these tips. If you have of your own beginner Horizon Zero Dawn hints, tips or tricks, please post them in the comments below.