I am trying to write a literary analysis on Susan Glaspell's Trifles, and I need a good thesis and direction to begin.

A good focus area for an essay on Susan Glaspell's Trifles would be the difference between how the male characters and the female characters investigate the crime scene. The male characters, as policemen and town officials, take a traditional approach, looking for evidence of someone breaking into the house or weapons used in the crime (Mr. Wright's murder). The women do not go to the Wright home to help investigate the murder, but rather end up doing so sort of accidentally; Mrs. Hale and Mrs. Peters are invited by their husbands to come along and help collect some items requested by Mrs. Wright, who is being held in the local jail. 
The women make astute observations as they look around the Wright home. They notice how Mrs. Wright was in the middle of a couple of kitchen tasks that she wasn't able to finish due to some unexpected event. They also look at a quilt that was in progress and see that Mrs. Wright made a few flawed stitches (Mrs. Hale actually redoes them for her, effectively tampering with evidence). The women infer that Mrs. Wright was upset by something that made her stitching erratic. They then realize that her birdcage door is broken and find a dead bird with a broken neck in one of Mrs. Wright's supply boxes. Using these details and their previous interactions with Mrs. Wright (Minnie Foster, before she was married), the women figure out that Mr. Wright killed Mrs. Wright's bird and she retaliated by killing him. They decide to hide this evidence so Mrs. Wright cannot be found guilty. 
While the women are the ones who solve the crime, the men never pay attention to the kitchen nor the quilt, because those scenes seem like "trifles" that only concern women. The daily activities of the home, mostly taken care of by women, are passed over by the men. In this case, though, the scenes of the home are the ones that reveal the truth behind Mr. Wright's murder.