I don't have a large garden, but I do plant tomatos and many different types of flowers anually. I have two preseason tips for gardeners.
1. Throughout the year, especially during the non growing part of the year, dispose of all your garbage in your garden. I keep a large plastic coffee can on my kitchen counter. I put all my garbage in it, coffee grounds, meats, rinds.......all garbage in it. It fills up about once a week. When it is full, I dig a hole in my garden and bury the garbage. I move the shovel each time I plant the garbage, so that I know where the next lot goes. Surprisingly, after about a month and a half, the garbage completely disappears. The reason being will be seen in tip #2. The garbage in the soil keeps the soil rich for growing things.
2. I'm not selling anything, but for the last 10 years or so, I've been ordering worms on line and planting them in my garden. I order about 1,000 worms anually, at the start of spring, mainly red wrigglers and Canadian night crawlers. These worms cost me about $50 anually and keep the soil well irrigated and, along with the garbage in tip #1, they keep important nutrients in the soil. If one desires, one can even start their own worm farm. I buy my worms from either Amazon or Jim's Worm Farm. See below:
Amazon.com : worms
Buy Red Wigglers Worm Composting and Vermicomposting supplies (unclejimswormfarm.com)
Those are my two tips for preseason garden prep.