If you are looking to capture all 400/400 pokemon in Pokemon Sword and Shield, here is our guide to complete your Pokedex 100%.
The process may take up to 100 hours of gameplay and some random trade links to get them all. For reference: https://progameguides.com/pokemon/sword-and-shield-how-to-complete-pokedex/
Organizing is a key factor, try to organize and rename your boxes with sections for Pokémon you need to evolve, ones you need to trade, etc. Make lists of what you need to do next, what you need to trade for.
Here is a complete Pokedex with locations: https://www.ign.com/wikis/pokemon-sword-shield/List_of_Pokemon_(Pokedex)
In Pokemon Sword and Shield, it is more likely to get 3rd stage evolution Pokémon in the wild. Many Pokémon including Gengar, Machamp, etc are possible to find in the wild. So, it is not recommended to evolve low-level Pokémons unless you are in a very late game and cannot catch it in the wild.
Here is a list of which Pokémon have strange requirements (other than leveling) to evolve them: https://www.supercheats.com/pokemon-sword-and-shield-walkthrough-guide/what-pokemon-have-evolution-methods
And a list of which Pokémon evolve specifically using stones: https://www.google.com/amp/s/www.gamespot.com/amp-articles/pokemon-sword-and-shield-stone-evolutions-guide-wh/1100-6471535/
Catching ditto as soon as possible is highly recommended, which can breed with any other female Pokémon. You will only really NEED to breed Pokémon to get all the baby (unevolved) versions that you can’t catch, such as Mime Jr., Bonsly, Wynaut, Pichu, Cleffa, Munchlax. Some Pokémon such as Snorlax, Sudowoodo, Wobbuffet, and Mr. Mime, only produce babies while holding certain types of incense.
Here is a guide on breeding including incense: https://www.polygon.com/pokemon-sword-shield-guide/2019/11/19/20971271/how-to-breed-pokemon-hatch-eggs
Related Topics: Pokémon Sword & Shield Review Thread
The absolute best tip for trading is to nickname Pokémon, what you want to receive in return. This lets a random person you are trading with and can’t talk to know exactly what you are looking for.
Use the guide below and make a box with all of your version exclusives, and try to trade them for what is on the exact opposite side of the list. You only really need 1st stage evolutions (less complicated to just evolve them yourself) and that can cut your list down massively.
The hardest ones to get are starters, as well as the 4 fossil Pokémon. You can be lucky enough to trade a copy they bred when using the nickname method to let them know what you are looking for. As for Zacian/Zamazenta, you should fairly easily be able to find someone who also wants to swap those.
Here is a guide with the Pokémon differences between each version: https://www.gamesradar.com/pokemon-sword-and-shield-differences-exclusives-starters-gym-leaders/
A lot of Pokémon are only available during certain weather patterns. If your goal is to finish your Pokedex quickly, waiting for it to change is not feasible. Luckily there is a way to manipulate this involving changing the date and time on your switch.