Sum of forces up = sum of forces down
Sum of forces left = sum of forces right
Sum of clockwise moments = sum of anticlockwise moments.
Remember these, you're singing.
Are your loads universally distributed, or point loads? This will effect the shape of the graph.
To draw a shear force diagram, you simply add and subtract moments.
Bending moments take into account the distance from the end you are working from, thus need to be multiplied into the equation.
UDL's create a slanting but straight line connecting points in a SFD.
UDL's create a curving arc shape between their start and finish in a BMD.
Point loads create a vertical line at the point they act, and are connected by a horizontal line, provided there are no UDL's acting between the points.
Point loads create slanting lines between two point loads in a shear force diagram, again provided there are no UDL's acting between the points.
Also, when working with a UDL in a bending moment diagram, ALWAYS remember you need to take into account where the load acts, ie, the distance from the node multiplied by half the distance from the point you are calculating from, and the start of the UDL.
Sorry if this is confusing, but it's very difficult to describe something like this without drawing it all out.
Good luck!
