Yeah D3D doesn't come with a math library so has no requirements really.
The way that you construct your matrices will have an effect on your HLSL code.
By default, matrices in HLSL are stored in column-major element order - e.g. for [column,row], the floats are stored in the order [0,0], [0,1], [0,2], [0,3], [1,0], [1,1], etc....
You can explicitly state the storage convention you want to use by using the appropriate keyword in front of your declaration, like this:
column_major float4x4 myMat;
row_major float4x4 myMat;
If you use the column-vector convention in your maths, then you'll write mul(myMat, myVec), otherwise if you're using the row-vector convention you'll write mul(myVec, myMat).
Edited by Hodgman, 05 May 2014 - 12:01 AM.