Many new members face a big task in clearing an overgrown plot. Don't be
afraid to ask for advice or help. Contact the site secretary on firstname.lastname@example.org
Is there a shed, a compost bin? How would you like to lay out your plot? You must leave the paths around your plot clear. Remember, you must apply to the Allotment Committee if you plan to build a shed or other roofed structure, or even extend an existing structure. But a fruit cage or polytunnel or greenhouse that aids you to grow crops is often a helpful addition to a plot.
You can rent a petrol strimmer from the Trading Hut. (This is a powerful tool for cutting through tall grass and thick weeds, using a rapidly rotating wire.) Being careful to remove any debris or objects before you start, strim down to the ground and assess what you've got.
If you plan to dig over the entire plot, as if it were farmland, you have your work cut out for you. It will help if you start in autumn, and cover the soil with weed-suppressing fabric or other opaque light-proof membrane. The cover will kill existing weeds and grass, and weaken or destroy their roots, leaving soil much easier to dig. Better yet, lay manure down and then cover the soil, leave it for a month or two, and you'll have added nutrients while killing weeds. As soon as you uncover the ground, it will begin to grow grass and weeds again--wherever you want to keep clear, keep covered.
Once you've cleared the ground, no-dig systems using raised beds are some people's preference--many timber or recycled plastic raised bed kits are available to buy online. Or you don't even need sides to your raised beds--just mound up the growing medium into beds with paths between them. This system can work for those who are not into digging, and it aids you in mulching and rotating crops through the growing season. Having paths between beds means you never have to step on the growing area, if you keep the bed narrow enough that you can easily reach into the middle to weed and plant. You may want to buy some topsoil and compost to top up your beds at first. There are bulk compost and top soil bags to buy, from internet sources, which can be delivered.
On 'no-dig' gardening, see Charles Dowding's website and books
For plug plants when you miss sowing dates or don't have time to sow your own seedlings, check out Delfland Nurseries (organicplants.co.uk) Sarah Raven (sarahraven.co.uk), D.T. Brown, or Robinson's Seeds.
You don't have to plant the entire plot all at once. Start with half, keeping the rest covered to suppress weeds and grass. Once you've got that under control, there will be no stopping you....