http://web.pdx.edu/~emch/ip1/bandcombinations.html

For Landsat 8, band combination are 564 (Land/water) and 654 (vegetation analysis)

For Landsat 7 TM you can use  4,5,3 band combination with the biggest difference

being that vegetation is green. This is the band combination that was selected for the

global Landsat mosaic created by NASA

Good bands are G R IR

I would suggest that use all bands because when we classify for land cover we focus all type of classes. For instance, Crop, Urban, Water etc. So if we choose specific bands, we are actually focusing a specific class, for instance, Green and NIR for vegetation. 

I think the best spectral bands to use for land cover mapping using TM is band 5,4 and 3.

Hi Souhaira,

I think the link below has got some good points on the band combinations for studying specific land features 

http://web.pdx.edu/~emch/ip1/bandcombinations.html

With optimum index factor (OIF) in ilwis you can find it

432 for natural color

welcome

you can use the green , red,NIR, and SWIR bands for this purpose

regards

Dr. Alaa G. Khalaf

Thank you

http://web.pdx.edu/~nauna/resources/10_BandCombinations.htm