There are a few distinct types of 'lag' and each has different causes. A good first step is identifying what kind of lag you're experiencing. That will go a long way towards finding a solution. This is a complex topic and it might be more than one thing you're seeing, so it might take a bit of fidgeting. It's also gonna be somewhat simplified otherwise I'm gonna be typing for a week. I'll order them in order of how common I hear people complaining about them
Rubber-banding
Symptoms: You find sometimes your actions 'undo', like run or walk a step and suddenly you're back where you were. Rare disconnections
Most likely cause: Intermittent packet loss
Fix: Disconnect from any VPNs. Ensure network drivers are updated. Check all network cables. Check there's no bandwidth hogs going on - anyone on the same network as you downloading giant files such as windows/phone updates, game downloads/updates etc. If you're using WiFi, try a wired connection
Regular Disconnection
Symptoms: Seemingly random and regular disconnections
Most likely cause: Sustained packet loss
Fix: Check all the rubber banding issues first because they are quick, but they are unlikely to cause sustained issues as severe as this. Check firmware on your router, replace it if necessary. If still having problems, ping and tracert to the game server and to Google to compare, use the results as evidence of degraded service to raise a complaint with your ISP
Bad Latency
Symptoms: Everything seems to happen 2 seconds after you requested it, everything seems delayed
Most likely cause: Jitter or high ping
Fix: If you're using WiFi, don't, unless you absolutely can't avoid it. If you're wired and all looks good, then it's probably an ISP issue, see the advice above relating to regular disconnections
Low FPS
Symptoms: Everything is in slow motion
Most likely cause: CPU overloaded
Fix: Run task manager and observe what else is using heavy cpu, end those tasks if safe to do so. GPU is also worth mentioning here, check your drivers are up to date, but not worth going deeper than that, this is not a GPU intensive game. Also, if you're on a laptop make sure you aren't in power saving mode. Check for overheating / airflow issues
Server Lag
Symptoms: Players and mobs all stop moving, sometimes for only a brief moment, sometimes longer
Most likely cause: Game server is having a stroke
Fix: Email GM 15 times per hour until he fixes it. Increase to 20 times per hour if it's the middle of the night, because that will definitely help
Slow Transitions
Symptoms: When you go from one map to another it takes a while for the new map to load
Most likely cause: Heavy disk usage
Fix: Open task manager and observe if anything is using a lot of disk IO (reads/writes, not storage). Most common culprits are windows update and antivirus scans, but these tend to be temporary issues. If you can't resolve it by closing/ending tasks, consider moving your Mir folder onto a different physical drive. SSD is a million times better than HDD. It's also possible that high memory (RAM) usage is affecting this, but less common, unless you have a really low amount of memory
I only lag when someone is pking me
Symptoms: This is a special kind of lag where everything is fine until someone catches me napping and suddenly I have 'lag'
Most likely cause: Skill issue
Fix: Pay attention and stop watching Netflix while in pk areas
