Ok, here's the methodology. A little hard to tell from the picture, but I assume B and C are pinned joints (i.e. can't support a moment) and A is a frictionless pulley (same thing, can't support a moment)
1. Draw each member (AB, BC, AC) separately without touching each other. In other words, explode the picture apart keeping the orientation of each member intact
2. At the ends of each member, draw forces in x and y directions and label them F1, F2, F3, etc. It doesn't matter which direction (+ or -) you place each force, as the correct direction will come out of the equations. Hint: at point A, you already know the magnitude and direction of the vertical force
3. In each coordinate direction (x,y), create an algebraic equation summing the forces. The sum must equal zero. You'll end up with 2 equations in the form of F1 - F3 + F6 + ... = 0
4. For moments, pick a point (A, B, or C) and write the moment equations about that point, making sure to properly keep track of the direction of the moment. You'll need the geometry to calculate the moment arms. I presume you know at least one of the distances AB, BC, CD. It is pure trig to find the moment arms. The moment equation also must equal zero. It will be in the form of F1*d1 - F2*d2 + ... = 0, where F's are the forces you labeled in step 2 and d's are the moment arms you calculate from the geometry.
5. In general, you'll end up with n equations in n unknowns, the unknowns being the F's. You may need to write moment equations at additional points if you don't have enough equations.
6. Solve the equations for the F's by combining equations to eliminate some of the unknowns and by substitution (system of linear equations).
This is tedious work, but straightforward. It is critical that you keep consistent with +/- directions for the F's.
