Wow, yeah. I found Member of the Wedding to be extremely dry and boring - obviously I opted to write on other texts.
But, I'll see what I can do/remember to help you draw on it

Firstly, as with all I+B texts, you need to consider:
- What identity and belonging are as separate entities;
- How they interact with each other (i.e. is one's identity define by their sense of belonging, or vice versa?);
- How identity and belonging is depicted in the text
With respect to Identity in Member of the Wedding, consider the differences between the intrinsic and extrinsic identities of the characters, as well as how their multitude of identities (or their singular, extremely personal identity (depends on the argument you make)) affect the way they interact with both the people around them and their environment.
On that note, we can see in The Member of the Wedding that Frankie is faced with a number of issues that confront her senses of identity and belonging. Firstly, the fact that she changes her name, and ergo who and what she represents (according to her, anyway), over the course of the novel reflects her lack of comfort with who she is. One can see this as a clear issue of identity. However, we can also see the effect of this lack of surety in identity through Frankie's lack of a sense of belonging. It is very much apparent throughout the novel that Frankie is not happy with her physical placement; she has few (if any) friends in her town, and longs to join her brother and his wife in the Alaskan wilderness. One may choose to note the physical disparity between these two locations (being Frankie's town and Alaska respectively); to Frankie, the town represents stagnation, boredom and a lack of opportunity to express oneself. Conversely, the Alaskan wilderness represents the unknown, something to which Frankie is drawn. In short, Frankie's dream is one of escapism; she feels that she cannot understand who she is or where she belongs in her home town, a place that she is overly familiar with.
It is also important to note the specifics of Frankie's vacillating identity; she states that she wishes people could "change back and forth from boys to girls". With this, and the conversational counterpoints provided by Berenice Sadie Brown and John Henry West, one can choose to further link Frankie's issues with Identity and Belonging to sexual and racial identity, and how Frankie and the others would perceive such notions in an American Southern town during the novel's time period. Note the lack of tolerance for deviation from the sexual and racial norm in these communities at the time.
Hope I helped!
p.s. I was lucky enough to do Bruce Dawe's 'Sometime's Gladness' instead for Identity and Belonging; they were the most beautiful, deep poems I have ever read (and not hard or draining to read like Member of the Wedding was!)
Best of luck for 2013.