To avoid such surprises, you will need to hand-pollinate your plants.
If you do not know how to do this, there are many books available
that cover pollination procedures for orchids.
Considering the large investment in time it takes to grow an orchid from seed, you do not want to spend all those years growing something that is not of good quality. I would strongly suggest that you know the parentage of the plants you will be crossing and recommend only crossing pure species or award wining hybrids. This means you may have to make a significant investment in purchasing the parent plants from reputable orchidists or suppliers.
You should not start with plants obtained from your local discount super store.
You need to understand the plants you raise will not necessarily all have the same flowers as its parents. You can even end up with many different variations of flowers out of the same seed pod. Because of this unknown factor, professional hybridizers prefer to use stem propagation whereever possible to keep all new plants consistent in blossom characteristics.
For information about stem propagation,
I suggest you read my article here
. Many of the techniques and materials used for stem propagation are the somewhat similar to materials and methods used for growing orchids from seed.