From our FAQ:

The upvote value given by SBI is determined by the amount of rshares in your SBI balance. There are multiple ways to get bigger upvotes from SBI on your posts:

• Enroll for more SBI units. The more SBI units you have, the faster your rshares balance accumulates. More rshares means bigger upvotes!
• Post less frequently. Even when you are not posting your SBI rshares balance is still constantly accumulating. This will result on bigger upvote value on your next post.
• Upvoting @steembasicincome posts. When you upvote @steembasicincome posts you get rshares added to your SBI balance according to the upvote value multiplied by 1.34 (temporarily reduced to 1.10x). This is even better than upvoting yourself!
• Delegating SP to @steembasicincome. You get temporary "bonus units" when you delegate to @steembasicincome. These bonus units give similar benefit compared to regular SBI units. Currently, you get 1 bonus unit for each 2 Steem Power delegation to @steembasicincome.