While there are many tips and tricks and techniques that will help you get better espresso - nothing is as valuable as paying attention.
What do I mean by pay attention?
I mean do each and every thing without thinking about anything but what you're doing.
I mean don't be distracted.
I mean watch the shot as it pulls, smell the shot, think about the shot.
Pay attention to the differences in your techniques and coffees and settings and pay attention to the result in the cup.
Pay attention to each shot and each drink over time - and pay attention to the big picture.
Too many people are thinking about their upcoming workday while making their morning espresso. Too many people are thinking about distribution while they are dosing. Too many people are talking on the phone while steaming milk.
Look at it this way... to reach a certain point in your growth as a barista you need to absorb, observe and learn X. Each time you pay total attention to the entire process of making a drink you absorb, observe and learn X/Y. If you're watching with 10% of your total attention... you've just taken a six month or one year or one decade process and multiplied it by 10.