If you need a good landscaper there are some simple things you can check to help weed out the bad seeds.
1. Are they licensed with the QBCC
2. Can they provide recent references
3. Are they properly insured
4. Can they proved a number of options for your situation, i.e can they quote rock, linkwall, concrete sleeper, timber sleeper, block as options for retaining walls.
5. Make sure you feel comfortable with the contractor before you engage them, you can usually tell if they are competent by the way they explain things to you. Always get more then one quote.
6. The price is important, just remember that cheapest is not always the best option. Some of the most expensive landscaping jobs I’ve seen started out with the acceptance of the cheapest quote!!
I hope this will be of some assistance with your landscaping project and your experience is an enjoyable one.