To skim assembly, first ignore all instructions except call, jmp (and all other branching instructions), and syscall, since other instructions are mostly either setting up the stack or preparing function call arguments. For each function call, backtrack to see what its arguments are and where they come from. For each branch (jmp/je/jne/…), check the previous instruction (typically cmp) to see what values were being compared. Try to draw a graph with the branches or use a graphical disassembler that can do graphs like IDA or radare2.