I never had to encourage my oldest to read, she loves it and is an avid reader. My other two are more active, and while they like reading there are often just other things they'd prefer to do. I find it helpful that our kids' school requires a certain amount of reading time for kids Monday through Thursday as part of their homework (they fill out a log and return it, signed, on Fridays). For my 9 year old son, for example, it's 15 minutes a day--it's long enough to practice, but not too long. Plus the requirement makes it just part of the daily routine.
A couple of things work for us. One is to use a timer. Our kids know that they have to read for at least 15 minutes, and with the timer they can be in charge of keeping track of that time. Another is to have a routine. One of mine reads in bed every night. One prefers to do hers soon after school. For one, it works best for him if we say he has to finish his reading before doing certain other things that he'd prefer to do (example: if he wants to play a video game, he needs to have his homework, reading, and chores done first).
Another thing that helps is to spend time looking for books that they really love. One of mine really only likes funny, goofy books like Bad Kitty. One likes funny, silly books with lots of action (bonus points for crude humor)--like Nathan Abercrombie Accidental Zombie, Diary of a Wimpy Kid, Franny K. Stein, Sir Fartsalot Hunts the Booger, or How to Train Your Dragon. He also enjoys graphic novels and scary books (like the Goosebumps series). One is into books about growing up, girls and friends, dragons, magic.
Awhile back I ran across a website with lists of books that appeal to reluctant readers, unfortunately I can't remember the name. You can probably find lists like this online, or you could ask your local librarian. One thing that I notice with my two who are less into reading is that books that are just giant walls of text do not appeal to them. They want something like the Dragonbreath** books that have plenty of text, but that also have funny pictures/drawings that break up that text. A book like this is more manageable, less overwhelming. (And these books are just funny.)
**(Also in this style, with pictures breaking up text: Diary of a Wimpy Kid, Geronimo Stilton, Franny K. Stein, How to Train Your Dragon, Captain Underpants, Zombiekins, and probably lots more that I can't remember at the moment. Maybe Time Warp Trio, which my kids enjoyed but we haven't read in quite some time.)