Set Development Roadmap

The following is a detailed road-map of most things you would want to consider while making an achievement set. It's not required to follow this exactly but is meant as a guide.

Initial Research

Game manual		Review
Game Faqs		Read/check
Game Cheats		Find, note
Longplay		Review/watch
Similar sets		Compare, note favorite ideas
Partimes		check if they exist
Speedruns		check if they exist

Conceptual Design

Achievements 1		Brainstorm, include ideas from similar sets, manual, etc.
			- Note secrets, progress, key events, collectibles, scores 
			benchmarks, Easter eggs, bosses, key items, par times. internal 
			rewards.
Research 2		Check/test that designs are possible.
Memory 1		Estimate needed addresses for achievements.

Memory hunt

Memory 2		Search for needed memory addresses.

Achievement Design

Balance	1		Balance set for difficulty distribution, remove or redesign 
			those that don't fit.
Achievements 2		Build the list, push complete to unofficial (not required).
Memory 3		Search for solutions missing, depending on the game's memory.
Achievements 3		Add new ideas as they come.
Achievements 4		Rework or remove ideas that are impossible.

Pre-release Final steps

Titles & Descriptions	Finalize
Bugs 1			Test achievements for bugs, possibly make/use movies.
Game page		Update. Game icon, images, info, resources, similar games.
Leaderboards		Code
Rich presence		Code
Badges			Create

Release

Achievements 7		Push to core
Points			Balance to your cap
Ordering		Do it
Forum post		Make announcement

Post Release

Bugs 2			Fix those that come.
Balance 2		Re-balance set difficulty based on feedback.