how to breed strong pokemon in pokemon diamond

[riolu]

howdo you breed strong pokemon in diamond

[Zidarose]

It is hard to be concise and give some good advice here, but I will try (and make a good recommendation on where to go to get the full details).

Breeding good Pokemon takes time as you need parents who are respectable themselves. You will also find yourself using IV checkers with fair regularity, as these are what will make a Pokemon stronger than average. Each Pokemon will inherit 3 random IVs from its parents and over the course of a few generations of breeding, you will find Pokemon with the appropriate statistics that you are looking for. Manipulating this is very hard to do, but these guides do have some solid information that will help a lot with the process:

This series of articles is the best I have found on the internet yet on the subject of breeding Pokemon. It will take time to read, but it is time very well spent:
The Breeding Guide Part I (D/P) - Smogon University
The Breeding Guide Part II (D/P) - Smogon University
The Breeding Guide Part III (D/P) - Smogon University
The Breeding Guide Part IV (D/P) - Smogon University