There is a few things you look for in a good knife right off the bat:
1. Materials.
When companies give you names of actual materials (Like titanium liners, S30V steel blade, cocobolo wood scales) instead of just "surgical stainless steel, metal handles, ect" Lower qualities knives are usually made of poorly cast pot metals done in factories with very little quality control, which means it wont have the strength and durability of a better quality knife. When you use better materials the edge stays sharper for longer, the knife is more durable, and it can look better aesthetically.
2. Fit and finish.
The knife should look seamless and all the pieces should fit together perfectly. If you can still see machining marks, flaws in the materials, edges that don't line up, ect you know whoever assembled the knife just didn't care. Where custom makes will take hours of fitting pieces to make sure they all line up flawlessly. The should be no (unless it's a D/A automatic) side to side, up and down, or back and forth play in the blade.
3. Lockup.
The lock should function flawlessly (usually after a slight break in period), hold tight, and be strong enough to take average use and light abuse. If it's a slip joint it should have excellent walk and talk (it should open solidly with nice click).
4. Manufacture and how they stand behind their product.
You know if you are buying a Benchmade or Spyderco you have an excellent warranty and some of the best quality control out there. When you buy from a custom maker you can see how well all their past pieces have been and expect what you're buying to be equal in quality or better.
That's the basics, there are other little things to look for, but generally once you've used a good blade extensively you'll never go back to the cheap garbage.
So yeah, I got a new knife
