I am a former installer and now currently on the distribution side, I could offer you this advice:
1. Start small. Don't try to tackle the big jobs yet. If you know someone else in the business, you could try to partner with them and learn what they do right...but be careful...make sure they are doing it properly.
2. Start with family or friends, just make sure they understand you are learning and the project might not be perfect.
3. Make a contact at your local distributor. I teach new contractors proper techniques all the time. I will always visit them at a job site if they need help (as time allows) and will put them in contact with a local rep who would be more than willing to help out and educate. Distributors will also hold installation seminars from time to time, attend them whenever possible.
4. Most of the bigger companies (Techo and EP around here) will offer seminars/trades shows over the winter. Attend them. The classes are valuable, but so is the time talking to the vendors and the contacts you can make with your peers. Ask questions.
5. You will need to buy some equipment, renting OK for others. You need a good compactor...don't skimp. Base prep is most important. A cut off saw is probably more important than a table top saw. A laser level is very important for proper layout. A skid steer or mini excavator would be nice...I would rent over buying in the beginning...I wish I would have bought a Dingo...would have made moving stone and material much easier.
6. Know the material in your area. If your distributor offers three lines, know all three. This will allow you to have a wide range of material to offer...but be careful. Each company has it's own quirks (i.e. Techo Bloc does not have independent corner block for it's wall units). Ask your distributor about new material when you are ordering. They should be able to explain the differences in the product lines.
7. Make your customer see LIVE product. Do not let them pick it out of a book. I tell all my contractors, if you can not bring your customer to my store, send them in...I will show them around and let you know what they have picked. There's nothing worse then finishing a project with a material your customer picked from a book and they say they don't like it. What do you do? If they can't see material live, you need to be very clear in writing that you can not be responsible if they do not like the product.
8. You need a contract. There are many threads on here about contracts.
9. Be mindful of customer changes...changes possibly mean more time/labor. You need to have a change work order as part of your contract.
10. "While your here, could you please do this...". Extra work means extra labor. Be careful you customer does not take advantage. You need to find the line of being service/customer oriented and making money. In the beginning, you'll do anything to get work and a reputation, but you still need to be profitable.