Staryus that are all around the same CP, but take a look at the two moves each Pokemon has when you catch it, and the power level of each move. If you catch a 98CP Staryu and a 105 CP Staryu, and the slightly weaker one has Water Gun and Psybeam, while the stronger one only knows how to Tackle and Body Slam, go for the better move set.
Next to each move you'll also see how much damage it does, along with a blue power meter for the second (more powerful) move, which indicates when your Pokemon's power move is ready to rock in a battle. Better moves, more power,
better Pokemon. You can always make up some CP points later
Can I Optimize Egg Hatching? And What's a Kilometer?!
While visiting Pokestops, you'll probably pick up some eggs, from which Pokemon hatch. But first, you need to incubate them, and then walk around. To do that, go to your Pokemon collection, and in the upper-right you'll see an Eggs tab. Tap that, choose an egg, then an incubator. Then you walk around and wait for the hatch.
Here's some advice: Don't waste your time incubating the 2K (kilometer) eggs unless you really want more low-level Pokemon (though that isn't a bad way to get a starter you missed or snag yourself a Pikachu). The 5K eggs can net you some decent ones like Cubone, Porygon, Machops, or Sandshrew. The 10K eggs get you more powerful, uncommon ones like Snorlax. Take a look at this handy infographic for a more in-depth egg breakdown, courtesy of Reddit.
You can even hatch eggs if you're on a bicycle, bus, or train. The app just registers that you're moving; it won't actually care that you're not walking. So, you can hop on your bike and keep the app open to not only get some exercise, but hatch some sweet Snorlax bros as well. Another great way to incubate and hatch eggs is to go for a run!
To pick up more incubators, you can either buy them outright in the real-money Shop or by getting lucky at Pokestops, though they are rare. You also gain more incubators and other more rare items as you level up. And remember: Pokestops replenish every 10 to 15 minutes, which is remarkably fast for a free-to-play mobile game!
By the way, 5 kilometers is about equal to 3.1 miles. Pokemon Go, not only does it bring us together, it educates.