Membrane proteins are notorious for being difficult to crystallize because they contain large hydrophobic patches on the surface and will aggregate instead of dissolving in aqueous solvent. Most membrane proteins that have been crystallized require detergents in the crystallization buffer to keep them from aggregating.  You can search the internet for another (membrane) protein that is similar in sequence to yours and that has been been crystallized successfully (and perhaps its 3D-structure determined by x-ray crystallography); the crystallization conditions used should be mentioned in the reference paper.  You can start from there for your own protein..