Hi, if these independet variables are continuous, you can standardize them before calculating your ANOVA (centring around zero and divided by the standard deviation) and afterwards the effect sizes / regression coefficient are comparable between predictors - they tell you how much the outcome variable changes for 1 sd change in each predictor. Based on this, I guess you can directly calculate some kind of "percentage influence" by setting the sum of the regression coefficients to 100 %. If you have only categorical predictors, you don't have to standardize but the definition of regression coefficients changes (they now tell you how much the outcome variable changes for changing the cateories of the predictor). That means of your predictors have the same number of categories, you can easily compare them. If you have a mix of continuous and categorical variables, I am actually not sure if it makes sense to compare them at all, since they are of different nature...