I'm not sure how popular at-home espresso actually is. I would imagine not very, since the cheapest machines are $500-$1,000, but one couldn't tell that from the fanatical circles that arise on the internet. For example, if you know what Coffee Geek is, you probably have an at-home espresso machine.
There are a few how-to's available online, most of them bad. And you can certainly find many tips buried within the annals of message boards everywhere, but even there, the tips are dodgy. There is only one tip that isn't frequently discussed but should be known by everyone who wishes to make coffee under pressure, be it Aeropress or full-on espresso: use fresh beans.
You always hear how fresh beans are important and to never buy beans from a grocery store. These bits of advice are usually said in the same breath as some hateful comment aimed at Starbucks being only for those who don't understand true coffee. But, truthfully, fresh beans for ordinary drip coffee isn't nearly as important as simply grinding them just before use. I've used Eight'O'Clock coffee beans for pour-over and gotten a more-than-acceptable cup of coffee, simply because I ground first.
Espresso is entirely different. Crema is impossible with old beans. You will only receive thin, watery espresso with only the faintest hint of cream on top. Not the rich, creamy, sweet, oily goodness of fresh beans. The thickness and body of espresso is entirely dependent on the freshness.
Likewise, since you're producing your espresso under pressure, you need evenness throughout the puck. Whereas with drip coffee, unused grounds from yesterday will do completely fine today, in espresso, the different moisture levels in the two masses of ground coffee will reduce your crema levels and make accurate extraction impossible. You will never get good espresso with grounds of different ages. For old beans, this is doubly critical since the moisture level in the beans is already low.
So that is the end of my tip. Only use fresh beans, and only ever extract grinds that have been ground at the same time.