Great espresso enthusiasm in this thread.
Are you ready to go further into the rabbit hole of espresso making?
Some other random tidbits that might be helpful if you've not already learned these...
The ground beans need to be used within 30 seconds before the grounds start to oxidize and thus change the flavor outcome of the espresso.
The espresso extracted needs to drunk within 10 seconds before the crema and flavor starts to change. This process is slowed by adding some other binding agent added (sugar or milk) to slow down the breaking down of the espresso flavor.
Tamping has been examined some in this thread but some might enjoy further discussion. The discussion around tamping is to create an evenly spread of ground coffee through the portafilter. The goal is prevent channels being created through the grounds which then leads to only those bits of coffee grounds being used to extract espresso. this leads to an overly bitterness of the espresso (also true in drip coffee, buys a whole different topic)
There are a variety of tamping techniques which can be used to create the best extraction if espresso.
I would suggest using that same kitchen scale to also measure the strength of your tamping which is typically suggested to start at 30 lbs of force.
Here is a great place to start reading more on tamping...this is only part one...
http://coffeegeek.com/opinions/coffeeatthemoment/10-07-2006
Cheers,
Mike