Pokemon Day Care
The Pokemon Day Care made its debut in "Pokemon: Red Version" and "Pokemon: Blue Version," and it is the most effortless way to level your Dragonair. Simply drop Dragonair off at the Day Care (locations vary by game) and leave. For every one step you take, Dragonair will gain one experience point. This may not sound like a lot, but over time it can add up. One drawback to the Day Care is that you must pay for its services.
Rare Candies
A rare candy gives your Pokemon the amount of experience points needed for its next level up. For example, if Dragonair needs 300 experience points to level up to level 41, then a rare candy used would be worth only 300 experience points. A drawback of rare candies is that they tend to be hard to find.
Trading
Many players only trade Pokemon to get them to evolve, but once traded, a Pokemon actually levels faster than a Pokemon that hasn't been traded. Pokemon trading can be done in all Pokemon games and requires a link cable for the Game Boy Color and Game Boy Advance, and a Wi-Fi connection for the Nintendo DS. Once traded, a Pokemon gains experience points with a 1.5 multiplier. This nearly cuts in half the amount of training you need to do, and it is good for leveling Pokemon with high levels of evolution like Dragonair.
Fighting the Elite 4
The Elite 4 appear in every Pokemon game and are the game's strongest trainers. Despite the name, the Elite 4 is made up of more than four members. It usually consists of four "main trainers" and one or two "champions." Fighting a trained Pokemon gives more experience points than fighting a wild one, and the members of the Elite 4 have the highest levels of trained Pokemon in every game.