JHH,
You have received some very sound advice. I'll highlight a few keys (some have already been mentioned by others):
1. Deal honestly...follow the Golden Rule
2. Cull aggressively, especially early on. We had problems (bad udders, dispositions, feet and legs, etc.) with many of the first purebred cows we bought, and later I realized that the breeders who sold them at the consignment auction were trying to get premium prices for their junk. Later on I found that these breeders didn't have real good reputations in the breed...sure wish I would have done more homework before I went to this sale. It was a bit painful the first few years culling cows that I had paid good money for just a year or two before, but after a few years, we had a herd with minimal problems.
3. Do your homework when determining who to buy cattle from (see #2 above).
4. Buy good quality from the start. If you pay a little more for better quality and buy fewer animals, you will be much further down the road to success than buying "o.k." animals but buying more of them. Typcially you can buy a whole lot better quality for another $500 to $1000 per head.
For example, when I first got back in the purebred business, many of the females that I bought I would give a grade of "B" (I'll use grades to make my example clearer). I assumed that if I bred them to the top AI bulls in the industry, those with a grade of A, I assumed that I would get a B+ or A- progeny. Many of these offspring would also be "B" and sometimes a "C". I can tell you from experience, it often takes several generations to breed up to an A herd when you start with B cattle.
5. Determine your market. Too often people think that they can be all things to all people in the cattle business. For example, they think they can raise top show cattle and still have a good product for the commercial industry. There are a few producers who are able to pull this off, but most can't. This is probably a subject for another discussion thread, but the fact remains that most show cattle don't work as well in commercial operations as the show folks would like to make us believe.
There is also a segment in most breeds who approach cattle genetics almost like an antique or classic car collector. When you read sale summaries in breed magazines and farm papers, these are typically the big money folks who spend $20,000 to buy a flush, or spend $50,000+ for a herd bull or donor. First of all you need big money to play this game, and many of these folks only stay in "the game" for 5 to 7 years, and get out when they realize that they are just trading dollars, and probably losing money. Many of these cattle, though they may have some good attributes, don't necessarily work in commercial environments.