Aerate your lawn
Pull small, regular plugs of soil to let more water, fertiliser and oxygen get deeply into the ground instead of simply running off.
Trimming in spring can stimulate healthy growth in most plants and shrubs, plus will help you contain the growth spurt from the Spring weather.
Get a handle on the pests now, before they take over your garden completely. Protect your plants with a coating of organic pest spray, and consider calling the pest controllers in like in this story here.
It's not a bad idea to get some professional help here, because having a professional weeding can often set you up for an easier weed maintenance season through to Summer.
Springtime is time to almost murder your roses. Treat your rose bushes like you hate them to get the best results.
If sections or your garden have gotten out of hand, Spring's a good time to transplant and give your garden more room to expand.