the answers to your questions depend on which small firm you go to. I would say that generally, you should expect around $12-15 an hour at a small firm. however, there are small firms that are paying summers at 1200-1600 a week (though mainly litigation boutique type firms) and clerks $30/hr. Hence, the starting salary will vary greatly also (likely between 40 and 100k). On average, I would guess that most small firms are in the $15/hr range and start at 40-45k a year.
I love working at smaller firms (I've worked at 2 "small" firms, different as night and day). You get tons of experience. My suggestion is to blanket your resume and build contacts. Professors, student organizations, clerkship (state judges love free clerks who will put in 10-20 hours a week) etc. are great sources. The jobs are hard to come by (small firms generally tend to not have a summer "program" but I was at a small (fewer than 10) lawyer firm with a few other summer associates, paying a nice weekly salary) and tend to be "as needed."
That said, find an area you like, utilize Martindale (though its outdated at times) or the Houston Bar webpage (firm listings with links by size) -http://www.hba.org/membership-100club.html - and focus on firms with practices that interest you. Also, remember that your success rate on small firms will be quite low unless you have a connection. Emailing or sending 50-100 resumes to firms will not be a stretch. Getting an entry level position mainly involves getting your foot in the door, putting out good work product, and making the most of opportunities (including hitting your employer up for a reference at another firm that may give you a better chance of an associate position - they will understand).
Hours depend not necessarily on firm size, but on type of practice. Litigation will be longer hours than real estate (generally speaking). Small firms will also have crazier hours - really long hours at certain times, short days other times - because they do not have hundreds of clients and hundreds of lawyers to divide work around.
Good luck in your search! Feel free to email me with any additional questions and I can try to give you more specific information (salary, hours, names, firms to try, firms to avoid, etc.)