How to select the best variables by RandomForest in R?

Question

I have a table of mRNA levels of my target gene and it's transcription factors in many different condition. What I want to do is to select the most important conditions and most important transcriptional factors. I used glm in R but I am stuck at the point that I can't extract the important data from it now. Could anybody help me please? I would like to use also Lasso, Elastic Net and Random Forest.

I've tried this:

data <- read.table("table.txt",header=T) 
genenames=colnames(data) 
attach(data_test) 
f1=as.formula(paste(genenames[5],"~",genenames[1])) 
glm(f1) 
glm.linear <- glm(f1) 
glm.linear 



        V1  V2  V3      V4    V5
1   3.85  3.85  9.41  4.31  9.01 
2   3.98  4.01  8.50  3.95  7.35
3   3.98  3.98  8.17  4.07  8.58
4   3.61  4.10  7.94  3.88  4.59
5   3.74  3.95  9.55  4.08  7.79
7   3.78  3.98  7.72  3.91  4.73
8   3.76  4.05  7.60  3.71  4.49
9   3.75  4.08  7.71  3.76  4.73
10  3.81  4.19  8.03  3.75  4.53