I've been struggling with my starter because I was fermenting dough for 24 hours in 70F to get some sour but that also strengthened the gluten and always gave an ugly looking tight crumb. Finally I increased the temperature to 73.8F and my baguettes came out with a nice crumb! except that I lost the sour. I think this is the reason sourdough bread is done in stages. Sorry for being a newbie, help is appreciated.
Two areas to practice on, forming and slashing.
Mark(mcs) has a great video on forming baguettes, check out the site below.
http://www.youtube.com/user/markcsinclair
As for slashing dmsnyder has a good tutorial on do's and dont's.
Sourdough dough is so much nicer to work with than normal dough IMO.