Can I improve how much I earn?
Your main mining power is your plots, they are the ones producing deadlines for you. Bigger the plots equals lower the deadlines, and lower deadlines equals more blocks mined by you. There is no other way to get lower deadlines, then simply having bigger plots! There are other ways to improve what you earn, one of them is stealing block from slow miners:
Example: If you found a 30 seconds deadline after 7 seconds, you would be able to beat someone needing 35 seconds to find a 5 second deadline
Other then that, there isn't a lot you can do to improve your earning, so don't expect something crazy.
Below is a list over things people have suggested. Lets see if they hold water.
Optimizing your plots
By optimizing your plots you reduce the time it takes to send your deadlines to the network, which could give a few extra blocks. You can find more information about optimizing here.
Yes, optimizing your plots helps to reduce your reading time, achieving the goal of stealing blocks from slow miners. Just remember, optimizing a SSD doesn't reduce the read time by a lot.
Use SSD(or SSHD) over HDD
As you can read here, SSD doesn't have any big advantages over HDD, it might actually be the opposed, because you can get more for your money if you are going with HDD.
No, get as much space you can get for your money. If you can get SSDs at the same price pr GB as HDDs, they would be preferred.
Mining with X miner
This might improve your reading time, but isn't a big deal most of the times. Like POW, if the miner is using the GPU instead of the CPU you will be able to read the plots faster.
Maybe, if you are able to use a miner compatible with your GPU use it over the CPU miner.
Using multiple GPUs to mine with
Same answer as above, but most of the times your HDD would be the bottleneck instead of the GPU.
Almost no, but it will only help if you are using a SSD or something faster.
Reading your plots with 2 miners at the same time
This will give you more deadlines, but the deadlines would be the exact same ones. This would also reduce your reading time, which could reduce your income even further.
No, looking twice at the same lottery ticket doesn't improve your chances of winning.
Using X pool over another
There might be some truth behind this one. Some pools prefer low deadlines over high deadlines by a lot, while other pools are more neutral. An example could be burst.ninja vs pool.burst-team.us. burst.ninja only allows very low deadlines, while pool.burst-team.us is allowing miners with higher deadlines to get a little Burst. This way big miners would want to join burst.ninja, because less money goes towards paying small miners who are hardly find any blocks, while smaller miners goes to pool.burst-team.us to get paid for all their deadlines. There is also the thing about pools taking a fee out of your earnings.
Yes, find the pool which fits you and has the lowest fee. Read more about pools here.