The most important single thing you can do is to be sure that you know how not to spread weed seed or propagules (any part of plant from which weed will grow). (See the section on Weed Hygiene).
Teach yourself how to control weeds. (See Find out How to Weed and Basic Weeding Techniques). See the section Campaign for Change so that you can help weeds and their control to be regarded as a basic ‘hygiene’ issue. This will help decision makers to justify what needs to occur to control their spread and reduce their impact. It is critical that this occurs soon, before the problem is insurmountable.
Find out who to contact about these issues; learn what invasive plants threaten Sydney, join a bushcare group or help an organisation that works to control weeds.