Answered by Shaykh Faraz Rabbani
“It should be noted, then, that there are three aspects to the intention: 1) the minimum legally valid intention, which is to firmly resolve to perform an action; 2) intention needed for reward, which is to also intend to draw closer to Allâh; 3) the time: it is a condition that the intention be made as one initiated the action, or just before it.”
[Please describe how one can perform the intention needed for reward and basically how 1) and 2) differ with respect to their application (i.e. the words or actions involved in them)]
The place of the intention is the heart. Pronouncing the intention is not in itself called for, though it is recommended if it helps one bring to mind a proper intention. [Radd al-Muhtar]
The minimal intention for validity is to resolve to perform the particular action. An example of this is the resolve to pray the obligatory zuhr prayer.
For reward, one needs to add to this some from of resolve to draw closer to Allah, such as fulfilling His command, seeking His pleasure, seeking to be a true servant, thankfulness, love, longing, and so on. “And a man only has that which he intended,” said the Prophet (Allah bless him & give him peace).