The first obvious advice is to have a good broodmare. You can have the chance to have a mare who's not very good but who will have a very good foal, but it's rare!
You need a mare who has great results in 1.30m classes. Mares who doesn't have results because they stopped their career after an injury can be good broodmares if they have a great bloodline.
It's really important to have great horses in the mare's bloodline, who were performing in 1.30 or 1.40 classes.
You also need a mare who is well shaped, because it's easier for non-professional riders.
A mare who moves well with a stallion you love, and it's a great start!
You need to know the pros and the cons of your mare, so that you can discuss with the owner of the stallion.
You also have to listen to your heart, if you have a mare you love who doesn't win big classes, you can have a foal with a really great stallion like Kannan!