Learn the Devanagri script. Many websites are available to help you learn to read and write the script. UK India maintains a "Learn to Read Hindi" site, and Archarya has lessons on learning to read Sanskrit. Both sites are free.
Utilize videos as you learn the Devanagri script and build your vocabulary. YouTube has Sanskrit lessons available for free. Search for "learn Sanskrit" for a complete listing.
Join an online language exchange such as ITalki or My Language Exchange. Use voice and text chat to converse with a Sanskrit speaker who wants to learn English. On some language exchange sites, you may have to provide English lessons in exchange for your Sanskrit lessons. Meet regularly so that your Sanskrit will improve over time. This service is free.
Hire a Sanskrit tutor online. Find a tutor on EduFire, ForteMall, Buddy School or similar tutoring sites.