Overview:
-Estimated achievement difficulty: 3/10
-Offline: 27 (750)
-Online: 17 (250)
-Approximate amount of time to 1000: 10-15 hours
-Minimum number of playthroughs needed: 2
-Number of missable achievements: None!
-Glitched achievements: None!
-Do cheat codes disable achievements?: No Cheats

An interesting mix of puzzle-solving and FPS, this game presents very little challenges given the fact that it's literally impossible to die. The biggest obstacle in your quest to 1000 will be finding a reliable boosting parter for the online achievements.

Introduction
Welcome to Prey. This game has a total of 44 achievements and requires two playthroughs to get 1000. The reason that two playthroughs is required is because the Cherokee difficulty does not unlock until you have beaten the game on the Normal difficulty.

Step #1: Playthrough on Normal Difficulty
Your first playthrough the game will be on the normal difficulty setting. When you begin the game you'll be on a level called "Last Call." After you're done insulting yourself in the mirror, head towards the bar. Your grandfather will stop you and say some words. After he's done mumbling, enter the bar through the two swinging doors and head up the stairs to the right to the arcade game machines (there should be four of them there). You're looking to earn over $250 in Black Jack and Draw Poker and 15,000 points in the Rune Man game. For Black Jack and Draw Poker always bet all of your chips. If you have a good hand save the game, if you don't reload the save and try again. Pac Man players should have no problem with the Rune Man game. Don't worry about the slot machine as there isn't an achievement for it. Doing this should unlock the three secret achievements Black Jack, Poker Face and Retro Gamer.

After this all of the achievements are either story or difficulty based so you can't miss anything. The game becomes even easier after level 4, Rites of Passage, because your new found spirit powers make it impossible for you to die. The game itself has some very interesting puzzle solving to go along with the normal FPS features. However, at some point you may get confused about what to do next. If this occurs I suggest you find a walkthrough to help guide you through that particular portion of the game. I found this walkthrough to be very helpful. After you have completed the game (22 levels in all), you must watch the credits. After the credits you will have a short little scene back at the bar and then have to go into a blue portal. After you enter the portal the achievement for difficulty and for beating level 22 will unlock as well as Cherokee Difficulty.

Step #2: Playthrough on Cherokee Difficulty
This playthrough will be a little tougher than the previous one for a few reasons. In addition to the obvious fact that enemies will be stronger, there will also be no health pods which means a lot more shooting souls in the spirit world. The entire point of this playthrough is to earn just one achievement, Galactic Hero. Again after you beat the game watch the credits and when you enter the blue portal, the achievement will unlock.

Step #3: Online Achievement Boosting
Overall the online community for this game is non-existent, so trying to do these achievements legit at this point is going to be quite a feat. Instead you should post/browse the game's Achievement Trading Thread here to find a boosting partner who wants to do all of the online achievements with you. Once you do that it's time to start actually boosting.
NOTE: You and your partner should be in a party before beginning the boosting process.

The first portion of the boosting will be done in player matches. One of you needs to create a player match with the following settings and then invite the other:
Go to XBOX LIVE --> PLAYER MATCH --> CREATE MATCH
Game Type: Team DM
Map: Roadhouse
Team Damage: No
Frag Limit: 100
Time Limit: None
Max Players: 2
Private Slots: 1
Once you're in the game it's now time to alternate killing each other 25 times with each weapon. I suggest you meet in an area that's easily accessible from all of the spawn points such as the basement or the bar. Also you can respawn right away if you press the after dying; this will greatly decrease your "waiting around time" while boosting. Replay the match with these settings until both of you have all nine of the "Reached 25 kills in death match and team death match using THIS WEAPON" achievements as well as both of the achievements for getting 250 kills in team deathmatch and deathmatch.
NOTE #1: The only weapons you may have trouble finding are the Crawler Launcher and Leech Gun. Both can be gotten on the second floor of the bar and are reached by going through the portal that is in the metal walled room off of the parking lot.
NOTE #2: The reason you're getting the 250 kill achievements here is because Team Deathmatch kills count towards Deathmatch kills, but the game will not allow you to play ranked Team Deathmatch with only two players.

It's now time to boost the ranked matches achievements. One player needs to create the ranked match with the following settings:
Go to XBOX LIVE --> RANKED MATCH --> CREATE MATCH
Game Type: Deathmatch
Map: Roadhouse
Frag Limit: 5
Time Limit: None
Max Players: 2
Once the match is created the other player must join by doing the following:
Go to XBOX LIVE --> RANKED MATCH --> CUSTOM MATCH --> DEATHMATCH --> JOIN YOUR PARTNER'S GAME
Now that you know how to play each other in ranked matches, take turns winning the matches (with 5 frag limit it should go fast). One you have completed 10 ranked matches in this manner you no longer need to play anymore. That's it! At this point you should have all 17 of this game's online achievements and thus be finished with your Prey online career.
NOTE #3: Sometimes one player cannot join another player's match, but vice versa it does work.

Conclusion:
If at this point you're still missing an achievement, it's most likely an online one. Revisit step three and if you have a good partner you should be able to knock it out very quickly.

[x360a would like to thank Method for this Road Map]