As others have mentioned, the plat guides are not worth it. A long time ago, there were some closely held secrets by a couple people for making plat, and they sold their ideas. Once a couple people purchased the guides, they told other people and the effect snowballed.
Since then, the "get-rich-quick" plat guides are useless.
My personal favorite is to head to Sol A and slaughter those filthy, red-skinned golbins for their FS weapons. Clearing the dungeon doesn't take very long at level 54 and you can net a good amount of FS and HQ ore, both which sell for 5-6pp each. Just bring a lot of containers. Zone out sell at the druid ring and head back in. Since Sony added a positive faction hit to the Sol A goblins, farming is decent also.
This is nice to get a little pocket change (couple hundred plat per hour). It helps the clerics peridot fund, food fund, minor spells, etc.
For the big cash...
You need to hunt in groups that have drops which you can sell. Most of the "good" loot is from higher level groups. So get the levels and start camping Ornate drops, Fungi, Flowing Slime boots, etc. All you need is one of these drops to get a decent chunk of cash.
Also, if you hunt in PoP zones, keep track of everything that drops (write the names down). Head to the Bazaar and search for all of those items. Now create another list of the good cash items. Next time they drop ask if you can have it. Most of the time people are ignorant to which items are good sellers.
For example, my cleric would loot everything in a PoTactics group. Right before I left I asked everyone in the group if there was anything that they wanted and I linked all the items. Everyone refused stuff, and that included two highly polished gems. Each gem is used in jewelcrafting and sells for 5-10k depeneding on the server. All the other trash loot sold for over 4k. Some people just don't realize the worth of items.
edit: fixed a couple grammar items, let other grammar items in to annoy people
Edited, Tue Mar 23 11:04:44 2004 by Wayen