Well, if you are looking for a specific character, be sure to ask CMs.
If you are able to do it- character meals are a fun way to meet the characters. Garden Grill at Epcot is generally the least crowded and will get you the most time with the characters. They might make it around to your table so many times you'll get sick of them!
Epcot is frequently the best place to get the least crowds with the characters because they are not always that visable. Last month, I went into Character Connection and walked right up to Mickey himself! Other characters are scattered throughout the World Showcase.
At MK, you will often see a large group of characters right around the train station in Town Square. The crowds here tend to ebb and flow throughout the day. If you want to go to Toontown, the best time is within an hour or so before park closing. The lines usually get much shorter. Sometimes they open the doors to all the rooms and have a free for all.
Another thing to try is when at AK, visit Camp Minnie Mickey right as a TLK show is starting- especially first thing in the morning. Everyone is going straight for the theatre so the character Kiosks don't always get noticed.
Please note the use of the words sometimes, usually, often, and frequently...these are only suggestions, not guarentees!
Good Luck!
