Well I have been studying up and am currently flying through an intermediate grammar book. I found a chapter on masc/fem and who knew but there are RULES! Why did no one tell me this before!!
So I'm going to do a very limited sum up here for those who are interested. Anyone who's reading who has no interest in french, stop reading now!
So all words ending in:
- age - except nage, plage, cage, page, image which are feminine
are masculine so are le or un e.g. le fromage
All words ending in:
- té - except côté, été, comité, deputé, paté which are masculine
- ence - except silence which is masculine
- ure - except mercure/cyanure which are masculine
are feminine so la or une e.g. une voiture
Then theres are some lists:
un- problème, système, programme, volume, modèle, groupe, domaine
une - couleur, odeur, saveur, peur, douleur
I'm not an expert I just found this today, but I thought it was quite helpful. No doubt its in no way exhaustive but its a start!