I don't mean my performance in Second Life. :) I'm referring to SL's performance on my computer - or maybe the performance of my computer in Second Life. To be precise, in this instance I'm talking about FPS (frames per second) and Ping Sim (time for data to transfer from my computer to the sim I'm in). You can get this information on the Statistics Bar - to find that go Advanced/Performance/Statistics Bar in V2.
I am no technical expert and what follows is only a description of what I did and the results. I'm sure everything I'm going to mention is glaringly obvious to most but there might be one or two people who haven't tried these things and for you this might be helpful. :)
Note that the steps I talk about can be undone, but if you're worried about making a fatal error please get real expert help before doing any of this. I seem to have managed the following changes without encountering any disasters - there was one glitch I'll discuss but it is manageable.
I have a fairly powerful computer and high speed access but there are a number of locations in SL where my lag seems unreasonably high - certainly higher than others I know. Standing on my Linden home my FPS would typically range between 11 and 14 - low. My Ping Sim time would range between 300 and 380 - high. I'm not talking about when you first arrive and have to wait for everything to rez - I mean once you've been there for a while and stabilized.
The Stats Bar in the photo at the top shows my readings after I made the changes I'll talk about below. My FPS ranged from 29 to 37 and my Ping Sim varied from 97 to 130. Huge improvements!
The first thing I did was update the SL Port Specifications. In my case I had to do this on my router - my software firewall settings were OK. Making these adjustments should be done by everybody in SL - it just makes sense.
The Wiki information is essential to you here and I'm grateful it's published. My only criticism is that the chart isn't dated so you have to check your settings periodically against what's published to see if there have been changes.
The next thing I did was very new for me but it was also extremely valuable. There were a number of unnecessary "Services" or applications running in the background on my computer. In addition a number of applications were launched at startup that I didn't know about or need. I still use Windows XP and using the System Configuration Utility you can access a list of both and turn off the ones you don't want. I'm sure you can find out from MicroSoft what utilties are needed in other versions of Windows. I don't know about Apple but I'm sure there's something. :)
In order to decide what I did or didn't need I compared the items on both tabs to information at this site. The only mistake I seem to have made (at least that I've found so far) is that I turned off something that allowed me to open my Corel Photo Editor - but that was easy to fix. On the top page of the Configuration Tool, I just clicked Normal Startup and rebooted. Then I had to redo my changes but I was more careful the second time. :)
I don't know if my experience will help anybody else. Frankly the attempt to do techie stuff makes my head hurt but the performance improvements in Second Life are worth it. :)