The first time I tried Earlibird in 2012, we had the wettest spring/summer and all my plot neighbours lost most of their sweetcorn that year. Mine went on to produce an (and most likely the only) amazing crop. Last year I grew Earlibird and Lark (in different beds far apart) - both were very good, but I have to confess that I did favour the Lark.
My tips include:
1) As mentioned, don't sow too early (and chitting is definitely the way to start the seeds off). I'm looking at 3rd week of April to early May and try to coincide sowing with a forecast warm spell if I can - seeds germinate quicker and plants get off to a good start in good warm sunshine, whereas seeds molly coddled along the way don't always thrive. I move them into the greenhouse /polytunnel if temperatures start to fall (the key as JayG mentions is how they sulk if left in prolonged low temperature - they simply just stop growing)
2) When planting out, dig the planting hole a bit deeper than the pot soil level - when back-filling, it will help to prevent the plant from falling over and encourages new roots to anchor down and take up water.
3) Give the plants a nitrogen boost by popping a handful (yes, a big handful) of chicken manure pellets into the planting holes - sweetcorn have to grow fast, flower and cobs mature in just a few months before the weather cools down in late summer. Think of sweetcorn as grass - the more you feed it, the quicker it grows
(and pray for lots of warm sunshine - lots and lots of sun)
4) Definitely keep well watered during the growing season especially in a heatwave but ease off when cobs are nearly ready
5) No matter how many years of experience, be prepared to get giddy with excitement when you can see the cobs are nearly ready for picking (and in case you didn't know, cobs picked should be cooked and eaten immediately to enjoy the sweetest flavours - in fact, so sweet you might be tempted to eat the cob raw there and then
)