How Do People Collect Colonials?
There are as many ways to collect as there are collectors. 
Type collecting has always been popular, and has seen a significant increase in interest over the last five years fueled by the advent of third party grading of colonial coins. Colonials can be challenging, and mysterious, and certification has simplified collecting and exposed it to a broader, more mainstream audience.
Within the definition of type collecting, there are basic type sets encompassing just one coin of each major series, to expansive interpretations that include one of every coin in the Redbook and beyond.
Historically, various colonial issues have also been collected by individual die varieties. The Connecticut and New Jersey series, for example, are comprised of dozens of major types (which are listed in the Redbook), but also by literally hundreds of individually distinctive die varieties (which are not in the Redbook). Such collecting is as popular today as ever, though it tends to be practiced by those collecting raw coins.
To date, the third party grading companies do not attribute slabbed coins by individual die varieties, though with the recent advent of certification of early half dollars by Overton numbers and Morgan Dollars by VAM varieties, we expect it will happen eventually.
And for those who find collecting individual die varieties an insufficient challenge, there are those who take it one step further and seek examples of die states which exhibit the progression of die wear through the striking of hundreds or thousands of coins.