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max_heap_table_size is the maximum size that a MEMORY table can be, if you don't use them or don't store much data in them (likely), you can reduce that without any problems. If you do use MEMORY tables, see how big they are and set it based off how much data is usually stored in it.

tmp_table_size is the size at which a temporary table (usually created for sorting the output of certain queries) gets converted to an on-disk table. Play around with it and monitor what mysqltuner reports for "Temporary tables created on disk". Also consider setting tmpdir=/tmp (as opposed to /dev/shm, as that is essentially just a RAMDisk, which won't help things much).

I'd also consider lowering wait_timeout to 20 or so, just to clear up unused connections sooner.

As for increasing things again, leave it for a couple of days and see what mysqltuner reports, I can try and provide some feedback on what it suggests. I'm assuming you're storing posts as InnoDB, so I'd start with slowly increasing the buffers there first for performance sake.

(2014-06-03, 12:35 PM)Cameron:D Wrote: [ -> ]max_heap_table_size is the maximum size that a MEMORY table can be, if you don't use them or don't store much data in them (likely), you can reduce that without any problems. If you do use MEMORY tables, see how big they are and set it based off how much data is usually stored in it.

What's a safe percentage of total memory I can use?

Well, if you're not sure what they are then I'm 99% sure you're not using them, so it shouldn't really matter what you set max_heap_table_size to. They're tables that are only stored in memory, so the data in them is lost when MySQL shuts down, they are only really useful for caching or temporary data (I have my mybb_sessions table set to Memory).