So, for our Theatre In Education about homophobic bullying, I created this African-American girl called Erica. She's from Houston and even though we're doing this to an 11 year audience and they probably won't notice if a mistake occurs, if I can better my skills, I will. So, what can I do to make Erica more authentic?
I don't know much about how African Americans, in specific, speak, but I'm pretty sure that a newish (although I actually have no idea what the timeline has been) trend for many southern Americans is to realize "Str" as "Shtr". So "strength" sounds a bit more... low and/or lazy, perhaps?
If you google accent database you'll find a number of sites with samples of a great variety of accents/dialects, such as these ones speech accent archive: browse Accents and Dialects of the United States of America | IDEA International Dialects of English Archive Plus, you can always look for interviews with artists who have that accent, I think Beyoncé is from Houston.
My best friend growing up was from Fort Worth, I don't think there are specific accents to each city. I know that many city dwellers in Texas don't really have a southern accent and have a standard american accent. The only give away was her mother would say "Howdy" sometimes, other than thought I would've assumed they were from Ontario; and that's in a different country. Her Dad had the absolute slightest Southern Accent, it'd be hard to pinpoint were he was from.