How to complete your Pokedex (Yes I have completed my Pokedex more then once)

1. Siblings or friends are a big part. Don't pick the same starter. Once you have completed the game and your starter is in it's final form put it in the day care with a Ditto, the egg will hatch into a starter duplicate. Trade with friends or siblings for their duplicates.
2. DON"T BE SEXIST! I have met many people who will only catch boys or only girls. Some Pokémon can only be one or the other. But they still are in the Pokédex so don't forget about them!
3. Don't know what goes in the empty spot? Search Pokémon Region _____ Pokédex number ____ on the internet. Bulbapedia is your best bet.
4. Can't get that legendary? Trade with your friends.
5. All you ORAS players listen to this. Pokédex number 210 is Jirachi. Which so far has only been in an event in Japan. Work around it. Check constantly for new events. PS we have all missed a few. (I was on vacation and missed the Eon Ticket)
6. DON'T LOSE FOCUS! Don't stop for a shiny hunt or for a chat with a random person.
7. Shiny Pokémon are incredibly rare! If you really want a shiny listen to this. By completing the Pokédex you get a shiny charm which increases your chances of finding a shiny.
8. Not enough evolutionary stones? Need a moon stone. Here is how to get unlimited of them.
Get Nincada (Ability compound eyes) then go to route 115 and search out Jigglypuff. It will increase the chance of finding one holding a moon stone. Don't forget a Pokémon with thief! So you can steal the Moon stone!

If this is helpful or you have more questions feel free to comment!