Could some one explain how to buy best cables?

As far as speaker cables go, you'll do just fine with a decent 12-16 gauge zip cord. Unless you're worried about aethetics. Otherwise you're wasting money. There's some good info at audioholics.com about speaker wires & snake oil.

A few things to remember.
1. Anyone can build a cable (no credentials of any kind required).
2. Once you've built a cable, you can essentialy say anything you want about the cable. The more money you have, the wider you can spread your message. No one monitors your claims for accuracy or truthfullness.
3. Different cables DO sound different, although some deny that this is possible.
4. It's up to you to decide if the Difference is better, a true improvement. This is dependent on your personal preferences, your system, your room etc., etc., etc.
5. A cables "sound", "character", whatever you want to call it, is not necessarily related to price. There are fine cables that range from modest to astronomic amounts of $$$.
6. Deciding which cables are best for you takes patience and hard work. Only you can decide who's peddling the snake oil.

When you are auditioning cables with a return policy, don't forget realitycables.com whose cables inserted in my different systems beautifully conveyed the character of each system. Does not tune a system, but lets you hear what is possible. You'll either be pleased with your equipment choices, or hear their shortcomings.
In a system that already makes you smile, get ready for a broad grin.
A unique cable philosophy from Auricle Audio Design delivers the lowest cost high performance cable I have yet encountered. Some of the auction prices have been so low that it demonstrates how hard it is to be taken seriously as a new vendor on Audiogon. I think being an early adopter of these has enabled other of my systems to deliver their best, and recommend including in any shootout, most especially the Signature digital IC.
This digital IC introduces no jitter as measured by Genesis Digital Lens detection circuit, a first in my experience, hinting at why it is so revealing, and "makes my entire CD collection sound brand new".
Tpsonic who initiated the responses in this thread pointed you toward the goal of educating your ears, and that is the fun part of our hobby, although at first it may seem you don't know what you are listening for, soon it will be obvious what you like with your own components.
I do think recommendations can point you toward something good to try, and then you will reach your own conclusion.

Just go to the Audiogon mart...you will find exactly what you need.

If the OP has not found cables after 16 years he/she sure has a lot of patience!