I have listed the forms for three verbs (खाना, पीना, करना).
First-person singular (मैं) :
खाऊँगा/पिऊँगा/करूँगा (m) and खाऊँगी/पिऊँगी/करुँगी (f)
Third-person singular and तू :
खाएगा/पिएगा/करेगा (m) and खाएगी/पिएगी/करेगी (f)
खाओगे/पिओगे/करोगे (m) and खाओगी/पिओगी/करोगी (f)
Third-person plural, first-person plural (हम) and आप :
खाएँगे/पिएँगे/करेंगे (m) and खाएँगी/पिएँगी/करेंगी (f)
You will notice that future tense forms mostly involve adding certain suffixes to the root form of the verb (what you get when you remove the ना from the verb infinitive). For masc. first person singular, we add ऊँगा, for masc. third-person singular we add एगा etc. The feminine suffix is just the masculine suffix with ी instead of ा or े at the end.
Just note that for certain verbs, the ending of the root may be slightly changed before you add the suffix. For example, for पीना, you add the suffix to पि instead of पी. Similarly, for देना, you add the suffix to द instead of दे for some forms making the masculine first person singular form दूँगा and so on.
Note: In all the forms which have ए which are not attached to a consonant, you also have alternate spellings replacing it with ये. Eg: खायेगा/खाएगा, खाएँगे/खायेंगे etc. Similarly, there exist alternate spellings with ओ replaced with यो or वो.