I like to start with a concrete representation, using manipulatives like unifex cubes, counters, or the units from our place value kits. I've also been known to use plastic bugs and people, pencils, counting bears...pretty much anything the kids can put their hands on. We pick a number, write it on our whiteboards, count out that many pieces, and then work to determine if that group as a whole is odd or even using a pairing strategy.
Usually working in pairs, the kids move the manipulatives into pairs. If every one has a pair, the number is even. (Later we write to explain how we know the number is even or odd.)
After a few practice times, we move into odd numbers. (I don't tell the kids that we're changing...I wait to see what they do!)
Then we pair them up, only this time there is an ODD MAN OUT! Poor guy doesn't have a partner, so this means the number is odd.
This is what we work on before moving to drawing pictures to represent a number and circling pairs.
This year I'm really putting an emphasis on the ones place from the get go, so as the numbers get larger the kids won't waste time drawing 47 dots and pairing them. They will only have to draw the digit in the ones place, and eventually just know that a number is even or odd. What a great way to practice place value, too!
After the kids complete a DOL (demonstration of learning), some move into an independent "funtivity" in which they practice what we've just learned, while others will be small grouped with me for reteaching. This is a file folder game that I call "Odd or Even Apples." It's so easy! The kids draw apple cards with numbers on them and use one of two strategies to determine if it is odd or even. Here is a picture of what the front of the file folder looks like:
And this is what it would look like put together:
And a close up of the back of my cards. What's great is that I make my cards self-checking, so they know if they are right or wrong. I would hate for them to be practicing incorrectly! I use a yellow highlighter on the reverse side to put an "e" for even or an "o" for odd. They typically work in pairs, so it's hard to cheat when you have an accountability buddy! You'll also notice small numbers on the backside with the answer. That number corresponds to a bag number to avoid lost pieces and mix-ups.
You can click HERE to find the files for the game. It includes the front cover, inside trees and instructions, along with three additional files for the even apples, odd apples, and blank apples, in case you want to make some of your own.