Use modern pieces to give a room an edge rather than a traditional bohemian feel. This space may seem casually assembled, but the color usage meticulously sticks to orange, blue, and green--tying in with the wall art. The rest of the space is kept quiet and clean.
Use an unexpected dark table to keep a space with much white from suggesting a cottage look or becoming too feminine. This choice here doesn't even look too eclectic because the finishes are kept to darks and whites--the table ties in nicely with the dark countertops.
Keep a room with varied furniture clean by using the same color throughout the different shapes. Note how the chairs draw on gray leather with clear detailing (tied together with the clear coffee table).
Stick to all whites (have you SEEN Maria's "Dreamy Whites? http://www.houzz.com/ideabooks/34128/list/Houzz-Interview--Maria-s-Dreamy-Whites) to allow for an endless conglomeration. In face, the more layers and textures, the better in this pristine and simple color choice.
Keep to a minimalism using raw elements to give a room a simple, natural feel. This room is tied together through the light birch finish of the table, armoire, and bookshelf backdrop. The red chair is the perfect pop.
Suggest variance with order by assembling a mix of furniture that sticks closely to a chosen color. Here, the array of brown and blues creates a nice variety without yelling for attention.
Combine. When several colors and finishes are combined, such as the whites, birches, and dark wood in this room, remember to tie each color in with something else. If too many elements stand alone in their uniqueness, the room will become bohemian and flea-market, which might be the goal. But keep things simple by tying everything together. For instance, the chair ties in with the lamp shade and colors in the textiles, the lamp base and desk tie in with the mirror's frame, and the white bed cover gets inspiration from the door and window dressing.
Use a motif, so to speak, in a smaller space. Here the common element among the many pieces throughout is the consistent existence of small patterns and pieces, and the blues that add yellow in small dashes.
Keep it simple. Now this photo does merge toward a more traditional bohemian look (and all of those cords would make me crazy--or trip) but what this room does excellently is keep a simplicity. Amidst the varied finishes of furniture and patterns of textile, the room is set up simply and each element sticks to a simple and straightforward shape.
Keep to a similar--not exact--wood finish match. In this light room with the crazy amazing green and wallpaper at the headboard, the wood is different but dark, helping ground the room and keep a pleasant variety. Though the headboard and frames and lamp are darker than the wall shelf and benches throughout, they all contribute to (rather than compete with) each other.
There is, then, of course, true bohemia. The collection of items accumulated from a free spirit who knows no home but the world itself. If this is the goal of your space: embrace it fully, go with it without reserve, and the wonderfully cohesive element will be fantastic randomness itself.