Do you have EPC control? Do you operate from the front panel or computer?
There is a purge button on the front panel, you turn the purge off at the beginning of the run, inject, and then turn the purge on at some point to sweep sample remaining in the inlet out the split vent. You may need to press the button several times to configure the timing, but the time you turn it on is dependent on the method. Probably after 0.5 or 1 minutes.
If you use chemstation you can configure this in the method.
Measure your purge flow using a flow meter attached to the split vent port on the front of the GC.
As far as the liner goes a "straight through" liner with glass wool works for most applications. If you have especially active compounds, or a wide boiling point range skip the wool. Taper or not is determined by the method. What solvent is your sample dissolved in? There are calculators available that tell you the expansion volume of your injection so you can be sure you're not exceeding the volume of the liner.
Here is a page on Agilent's site that talks about the reasoning for some liner features:
http://www.chem.agilent.com/en-us/produ ... 18299.aspx
Here is a list of liner part numbers:
http://www.chem.agilent.com/en-US/Produ ... icing.aspx
5181-3316 is probably what you want.
