Help and suggestions needed

Hi Fellow Minecraft players and server hosters,
I have recently opened a bukkit server for my friends,
we are around 10 friends average online players at the same time is 2-5 maybe even 6,
I run the server 24/7.
I'm running the server with 5 GB RAM out of my 16
I'm using windows 8 64 Bit
i5 3370k
gtx 670

My friends and I have felt some lags recently,
How do I improve performance and maybe add some nice recommended plugins.
Server info:
5 GB RAM
Bukkit Server 1.6.2
Online almost all day every day
Plugins:
Essentials
Waypoints
Essentials Chat
Essentials Spawn
AutoSavePlus

Awaiting recommendations thanks in advance

 

I just ran my server and it didn't work.
localhost works but external ip doesn't
I changed ip and updated the port forwarding still doesn't work help

 

Type this in cmd. ipconfig. See if that is your local ip as you set in portforwarding. If not change it. If that doesn't work try checking the ports for both your server and portforwarding.