First of all, I sow about a third too many seeds. This allows me to have extra to choose from when planting out. The more uniform the plants are when planted out, the more likely they are to be at the same stage when pollinating, which helps.
Also I like to have reasonably big plants to put out, decent little strong stems on them as opposed to smaller weaker plants. I find that sowing into 3 inch pots, then potting on to 5 inchers is the only way to get them that bit bigger.
Lots has been written about corn not liking root disturbance, and therefore using loo rolls to sow in and plant straight out. The problem with that is that they need planting out when the roots come out of the bottom, even if the weather is not right or the plants are still small.
If in pots and the roots start coming through the bottom, I just tip the plant out, and put it back in which tidys the roots back into the pot again. So long as the roots are not damaged they will grow away strongly when planted out.
Earthing the stems up a couple of times in the season helps too. The corn will root strongly from the base of the stem, meaning more nutrient uptake and plants that are much more anchored in windy conditions.
As they are reasonably shallow rooted, the patch should be fairly rich, with plenty of organic matter forked into the top layers.
You can also plant squashes and pumpkins nearby to grow through the corn blocks. The stems of the squashes will grow through the corn patch and shade the shallow roots, minimising water loss, and you will get a crop of squashes or pumpkins from it too.
Totty