You need to know which egg to incubate.

One of the more exercise-focused aspects of Pokémon Go is hatching eggs. Each egg has a distance meter next to it, and when you put that egg in an incubator it becomes active. When you walk the distance marked on the egg while playing the game, the egg will hatch and you'll get a brand new Pokémon with a bunch of Pokémon Candy for that creature.

The difficult thing here isn't the walking, it's choosing which egg to incubate next. You only get one incubator with unlimited uses, and every other incubator — whether purchased or received from a level up — has a three use limit. The best way to choose which eggs go in which incubator is to know which Pokémon are in the egg to begin with. While there's no what to know exactly which creature is in your specific egg, here's a list of Pokémon and the egg types they show up in.

ID Name Distance
001 Bulbasaur Bulbasaur 2km
004 Charmander Charmander 2km
007 Squirtle Squirtle 2km
010 Caterpie Caterpie 2km
013 Weedle Weedle 2km
016 Pidgey Pidgey 2km
019 Rattata Rattata 2km
021 Spearow Spearow 2km
025 Pikachu Pikachu 2km
035 Clefairy Clefairy 2km
039 Jigglypuff Jigglypuff 2km
041 Zubat Zubat 2km
074 Geodude Geodude 2km
129 Magikarp Magikarp 2km
023 Ekans Ekans 5km
027 Sandshrew Sandshrew 5km
029 Nidoran♀ Nidoran♀ 5km
032 Nidoran♂ Nidoran♂ 5km
037 Vulpix Vulpix 5km
043 Oddish Oddish 5km
046 Paras Paras 5km
048 Venonat Venonat 5km
050 Diglett Diglett 5km
052 Meowth Meowth 5km
054 Psyduck Psyduck 5km
056 Mankey Mankey 5km
058 Growlithe Growlithe 5km
060 Poliwag Poliwag 5km
063 Abra Abra 5km
066 Machop Machop 5km
069 Bellsprout Bellsprout 5km
072 Tentacool Tentacool 5km
077 Ponyta Ponyta 5km
079 Slowpoke Slowpoke 5km
081 Magnemite Magnemite 5km
083 Farfetch'd Farfetch'd 5km
084 Doduo Doduo 5km
086 Seel Seel 5km
088 Grimer Grimer 5km
090 Shellder Shellder 5km
092 Gastly Gastly 5km
096 Drowzee Drowzee 5km
098 Krabby Krabby 5km
100 Voltorb Voltorb 5km
102 Exeggcute Exeggcute 5km
104 Cubone Cubone 5km
108 Lickitung Lickitung 5km
109 Koffing Koffing 5km
111 Rhyhorn Rhyhorn 5km
114 Tangela Tangela 5km
115 Kangaskhan Kangaskhan 5km
116 Horsea Horsea 5km
118 Goldeen Goldeen 5km
120 Staryu Staryu 5km
128 Tauros Tauros 5km
137 Porygon Porygon 5km
095 Onix Onix 10km
106 Hitmonlee Hitmonlee 10km
107 Hitmonchan Hitmonchan 10km
113 Chansey Chansey 10km
122 Mr. Mime Mr Mime 10km
123 Scyther Scyther 10km
124 Jynx Jynx 10km
125 Electabuzz Electabuzz 10km
126 Magmar Magmar 10km
127 Pinsir Pinsir 10km
131 Lapras Lapras 10km
133 Eevee Eevee 10km
138 Omanyte Omanyte 10km
140 Kabuto Kabuto 10km
142 Aerodactyl Aerodactyl 10km
143 Snorlax Snorlax 10km
147 Dratini Dratini 10km

And that's it! From here you can plan out which eggs would be best for you to hatch right now. For example, focusing on 2km eggs is great if you are hoping to quickly level up a starter Pokémon, and 10km eggs are great if you want something unique. The only uncertainty with these eggs is Candy.

The amount of Candy you get from each Egg is random, somewhere between 5 and 35 Candies. That could mean you get an Eevee with everything you need to evolve it on the spot, or it could mean you get a Pidgey with 5 Candy that makes you sad on the inside. Either way, hatch as many as you can!