First, you need a location with 9 rooms/spaces. In a house with a large number of rooms, corridors and stairs might be considered dead spaces, but in most instances, these will have to be considered rooms. (After all, couldn't a murder take place in a stairwell? That seems to make sense.) Second, you'll need to select 6 weapons you have around the home. Don't worry if these are ridiculous; my own apartment used the cat and a Doctor Who scarf in addition to a sword and a sharp letter opener. Put each Weapon in a different room, ideally one that suits it (the Potato Masher in the Kitchen, for example). There are no secret (warp) passages unless the space actually has them too.
The cards representing each location, weapon and suspect are obviously the biggest challenge. I used my Photoshop skills, took pictures of each room and weapon, and poached pics of the potential players from Facebook, then printed them out on soft cardboard. If you just don't have the technical capacity to do this, you can of course use your normal Clue cards as stand-ins. The Study becomes your bedroom, the Conservatory is the bathroom, the Candlestick is the heavy shoe you plan to use as a weapon. If you ARE making your own cards, have fun with your Suspects. As much as possible, these should be the people living in the space and those who you plan to play with. I made more than 6, but only 6 can play at a time. Select pictures that make these people look either sinister, crazy, or like detectives. Don't worry if someone comes 'round to play who DOESN'T have a card; they get to play another character (if your pets have cards, that can be an amusing role for them to play).
Each player will need the following: A 6-sided die, pencil and paper (you can prepare the grid with all the possible clues in advance), and of course, their share of Clue cards. Costumes are optional.
Finally, you might want to clean your room. There are gonna be people in there, at some point.
This isn't about Colonel Mustard and Miss Scarlet, whoever those people are, having killed Mr. Boddy or whatever. This is about YOU, and whoever YOU might have killed. A bit of black humor here, but the group should decide who the victim is. It can be a real person who generally pisses everyone off, or if that's too macabre, it can be someone famous/infamous, a historical figure like Hitler, or a fictional character that annoys you. Regardless, your own personal game should never kill the same person twice. If less than 6 people are in play, you still need 6 suspects. If you DO have more than 6 Suspect cards to choose from, select the needed character(s) based on who hates your chosen victim the most. This may all seem very dark, but it makes the game more personal and will inspire fun gallows humor, trust me.
Before putting cards in the solution envelope, shuffle the Room cards and let each player pick one. That will be the room they start in. Also shuffle a number of standard playing cards equal to the number of players and let them pick one of those. These should be one each of the Ace, 2, 3, 4, 5 and/or 6. Remember, since you're actually moving around a space, you won't be at a table. These cards decide the turn order AND which player must show you a clue at any given time. Roll your die, and highest starts, play then moving from that number as if the next were to one's left (so when #3 suspects something, #4 must show them a card, then #5 if they can't, and so on; play will they move to #4).
Movement: When it is your turn, roll your die. You may stay where you are OR move a number of spaces (each room counts a space) according to the following scheme:
1: You cannot move
2-3: Move 1 space
4-5: Move up to 2 spaces
6: Move up to 3 spaces (which should get you almost anywhere in a normal house/apartment)
Weapons: You can only suspect a Weapon that is in the Room where you are, so there's an additional difficulty (meant to counterbalance the ease with which you can get to almost any Room fairly easily) - you must move Weapons with you. This means you might have to waste time/movement getting to a Weapon and bringing it to the appropriate room. You don't need to stop to get a Weapon, you merely need to walk through its Room.
Special Pet Rule: If you're using your pet as a weapon, you don't want to traumatize the poor thing any more than you need to by trying to catch it and lug it around the game space. So you'll need a stand-in (a stuffed animal, for example) which will represent the pet/weapon in the game. BUT, and this is a fun bit, if you happen to be in a room where the actual living animal IS, then you may consider it present for purposes of suspecting its use in the murder. If the animal likes to roam, all the better; it adds an element of chance or, if you know how to call the pet to your location, of strategy.
Suspects: You do not need to fetch people in the game like you do Weapons. You simply call out their names, and they must move to your location (just as in the real game). When a Suspect is moved this way, they cannot bring a Weapon with them. If the Suspect isn't playing, then simply evoke their presence; they don't need an object to stand in for them.
Suspecting and Accusing: As normal. You WILL have to move to show your Clue cards to other players, but of course have to return to your starting point (and again, you cannot bring Weapons with you while showing cards, though you could life all these "weapon smuggling" bans for a more treacherous game). Leave the solution envelope in one of the Rooms; players who accuse can of course go to that room and check if they were right.
This all seemed to work, and was jolly good fun (and you can add to it by calling a Suspect to the Bathroom, where you are standing behind the shower curtain, playing with genre tropes like that). One of the challenges is making yourself heard from the darker corners of the house. Make sure you can communicate with everyone without having to scream, and every player does need to hear everything that's going on, even if they can't see it. One solution in larger spaces is social media. Players have been in the same Clue chat, for example, and text each other their suspicions. Similarly, you can remove a lot of unnecessary movement by texting the Clue card you want to show. As an optional rule when playing back to back games, we decided to leave the Weapons where they currently were, and not return them to their starting positions (so long as there was still no more than one in any given Room), which naturally changed the strategy each game.