You probably know all this Dim, but in the interest of some discussion around the topic here are some thoughts
Crop rotation. I make a 4-year crop rotation. Needs a fair bit of space to achieve that ... and the biggest problem most people have is that each zone doesn't warrant an equal amount of space.
For example, most Brassicas are planted about 2' apart in each direction, so take up lots of space. A few Sprouts, Cabbages, and some Sprouting Broccoli for the Spring and that's a lot of space.
Spuds also take up a lot of space - maincrop are cheap to buy, so one solution is to only grow Earlies.
My solution is to have 8 beds, rather than 4, for crop rotation. 4 beds for conventional rotation, and then the other 4 beds have 1 x Brassica overspill, 1 x Spuds, and 2 x Cut flowers. That way I get twice as much space for Brassicas as the others.
Next up is choices on what to grow. Assuming you don't set about growing "everything you eat" then I would recommend focusing on a couple of areas:
1. Crops that are high-cost in the shops. Early Spuds, Runner Beans, Soft fruit perhaps, Asparagus if you like that (and have space to dedicate to it)
2. Crops that you like to eat. Don't bother growing stuff that you saw a pretty picture of in the shop, or have heard of but never eaten but think you should try. I have no idea why seed companies have plenty of packets of Asparagus Peas, Scorzonera, Salsify and the like. I've grown them all, they aren't worth the effort. If they are, already, your passion then that's different - they would then fall under "crops you like to eat"
3. Crops with good flavour. Avoiding Supermarket varieties (often selected to make a uniform and easy harvest-in-one-go for the farmer, and with thick skins that don't bruise easily etc. which are often detriment to flavour) you can choose varieties that you like the taste of (that might take a year or two of experimenting, unless you have bought specific named varieties in the shops that you have liked). You might also choose to grow varieties that are low yielding, or more disease prone, but which you like the flavour of.
Sweetcorn is one of the major winners - pick it straight into the pan, don't store it. As soon as it is harvested the sugars start turning to starch, so its much sweeter if you cut & cook immediately. Can't do that with Supermarket Corn of course, its been travelling for a couple of days, minimum, before it gets to your home.
4. I use a maximum-faff method (well, its considered high-faff by other people, I would argue that it isn't as bad as it seems
). I sow almost everything indoors, grow on in 9cm pots, and then plant out. I'm on heavy soil here, its impossible to get it into workable state early in the season most years, and in a bad year, like Spring 2013, the weather can put you a long way behind. For me the benefit is that I can sow, and prick out, in the evening after work on any night that I choose (well ... so long as I can swing the use of the kitchen table for "gardening" past Mrs K!!). Then when soil is right I can plant out. This is obviously more work than just sowing a row of seed direct into the soil. However, when I plant out I hoe off the weeds and the plants have a huge head start on them, and weeding is trivial thereafter (whereas if I hoe and sow then weeds and crop come up together and hand weeding them is fiddly).
I sow only a few of each variety. For example, Cauliflowers will only "stand" for a week to a fortnight once "ripe". We eat a max of 2 cauliflowers a week, so I sow 4 cauliflowers (in my 9cm pots) twice a month. We therefore have a steady stream of harvest. I don't have a nice smart row of Cauliflowers ... I have 4 of them, then a few something-else, and then the next batch of 4 Cauliflowers
Similarly with Lettuce, Beetroot, Kohl Rabi, and so on.
I also don't have any gaps in my rows / blocks. Lots of people grow Broad Beans overwinter (sowing outside around now). My experience was that in bad, wet, winters I lost half or more. I sow mine, in 9cm pots
in January and plant out in late February / early March. They are hardly any later cropping than Autumn sown ones, but I have no gaps in my rows, thus I have exactly the number of plants I want, which overall works out more efficient on use of space.
Another benefit of raising in pots is that the next crop is coming on before the earlier crop has finished harvesting. its about 6 weeks from sowing to planting out, so I don't need the ground to be available until 6 weeks after I sow in pots - again, I think that is better space utilisation, particularly later in the season when I am growing Chinese greens etc. for late Summer / Autumn harvesting, and as a follow-on crop for early Spuds and the like.