I'm a bit of a one-track mind - "Take some lessons" is the only advice I consistently give to starters in this business, because I know what it's done for me.

I spent about 10 years doing backing and occasional lead vocals before taking lessons (at night school with 20 others!); my absolute vocal range hasn't changed but it sure sounds better, is more usable at the extremes of its range (especially the low end), and I am much less prone to strain and sore throats. I cannot emphasise enough the degree to which vocal lessons have made the job easier.

And this doesnt just apply to the rock end of the repertoire. The improvements in pure physical mechanics that I learnt at the lessons has audibly improved the quality of my voice at low sound levels due to the greatly improved control.

Ultimately, do whatever works for you, but it must be comfortable and natural.