In some areas allotments are like gold dust and there are long waiting lists. You may well be able to get around this by choosing another site or simply offering to take on an overgrown plot. If not, the good news is that an authority believes there is a real demand, it has statutory duty to provide a sufficient quantity of plots to lease them to people living in the local area.
The government website helpfully points that out 'If local people feel there is a need for allotments which is not being met, they can get together a group of any six residents who are registered of the electoral role and put their case to the local authority'. You may find that you get six people together just by spending a Sunday afternoon at your nearest allotment. Alternatively you can put posters up at existing sites, in your library, local pub or anyway that may be of interest.
The National Society of Allotment Gardeners can offer helpful advice on getting the local council to take notice, and imagine the sense of satisfaction you'll get from knowing you were instrumental is creating a brand new site!
Alternatively, if you want to get planting right away you could approach a neighbour or an existing allotmenteer who looks like they are struggling with their plot, and tactfully offer to lend a hand. They may well be delighted with the help and you can share the fruits of your labours, as well as tasks like watering and weeding. And unless you have a large family, a half-plot may be better suited to your needs at first. It's well worth remembering that allotment sites vary in the facilities they offer, the rules and regulations they enforce, the rent charged and their attitude towards children, women, organics and so on. If you have a choice of sites, check them all before making a decision. Talk to plot holders to get a 'feel' of the place.
Location- Close to home, ideally within walking distance, is the most practical, and the most likely to retain your enthusiasm.
Check the sites rules and regulations- If you want to plant fruit trees, keep hens, paint your shed, use plastic mulch or grow flowers you may not be able to on some sites!
Do you hate bonfires? Some sites don't allow them; others restrict burning to certain days of the week
The cost- The average annual rent for an allotment plot is ?5- though rents can be as little as 50p or as much as ?00. This usually includes the cost of water, but may not. They may also be reductions for pensioners and people on benefits
Organic plots- If you want to grow organically ask if there is a specific 'organic area'. Don't be put off if the answer is no. You can still run a successful organic plot, and, as you may succeed, others may follow. Organic vegetable gardening is very important for a lot of people.
Good society- Some allotment sites have a very active community with a trading shed, a meeting place or mentors offering to help newcomers for example.
Vandalism- By their very nature, allotments are at risk from vandalism. Ask about this!