before putting the muclh down, either mechanically/physically remove all the weeds or use a herbicide such as round-up.
Fabric may help for the first year, but in general, as most will agree here, does little to prevent future weed growth.
After installation, the best thing is to do periodic maintenance, either by physical pulling or by chemical. The key is not to let it get out of control.
nothing is 'maintenance free' in this world. Mulch doesn't mean you can put it down and walk away from it. You need to keep a maintenance plan and will need to most lilkely re-mulch every year.