I used to ride my bike 10 miles to and from work. total of 20 miles/day in michigan weather. even winter.
#1 rule is::::
have a destination. do not set a time limit because if you do it will get boring. If you set a destination and a reward at that destination (ride to the mall and have a milkshake when u get there)
#2 rule is::::
USE an MP3 player or CD player. If you do not do this the ride will also get boring. Music sets most of us in this trancy enviornment. I could ride forever if I had a good playlist going.
#3 rule::: Safety-- I don't use helm's blah blah but I've been riding forever and stuff. Not to mention im stupid. Humans are squishy. Use a helmat.
#4 Bikes---
there are a few different ones. I am currently using a street bike. Skinny tires:
pro: Faster, lighter
con: have to be really careful of where you ride due to skinny tires, no shocks, no jumping curbs.
Mountain bike-- I used to ride this for last 5 years, my favorite due to some models have shocks that even seperate both ends of the bike. so u can pretty much go on any enviornment:

(that was mine in Michigan)
pros: go anywhere do anything bike
cons: heavier/slower
It all depends what you want to do and where you are going to ride.
Overall I prefer a seperated mountain bike due to versatility
this has been a stikes review.
the end.