Linear: Address your residual plot. Does the plot show a random scatter of points?
Independence: Is your sample size less than 10% of the population? (skip if sampling without replacement)
Normal: Address your residual plot. Is the population of residuals normally distributed? (no strong skew or outliers)
Equal SD: Address your residual plot. Is there roughly the same variability at each x value?
Random: Does your sample use random sampling or assignment?