Most of us in the Northern tradition don't believe in worshipping any of the Norse deities, and we find that (*UPG*) most Norse deities don't want to be worshipped. Honoring them, however, or including them in your work is another thing entirely.
Your first step would be to read through the literature. Namely the Poetic and Prose Eddas, and some of the Sagas, as I feel that this gives you the best insight into the Gods and their role in the pantheon. After this, you should set aside some time to determine which deities specifically you are interested in (or which pantheon set you might be more interested in). Spend some time studying and reading up on those specific deities to learn more about them.
Once you've established a base of understanding of that specific deity, you can move on to giving offerings. Offerings will depend on which deity you choose to work with, and what pantheon they fall under.