sops, dops, pops, rops, vops, shops and chops?!

My first few weeks was spent watching and doing a lot of tutorials.  There were a few things I had to get over when I was first started out using Houdini

1. The language - learning what sops, dops, pops, etc means.  Almost any Houdini tutorial you watch they refer to these operators
2. The network - going in and out of networks and which nodes belongs to which
3. Expressions, variables and scripts are your best friends
4. It's just not like maya - get over it and keep an open mind

Helpful intro tutorials:  Go Procedural Intro guide from SideFX and Houdini+Fundamentals from cmiVFX.  

Houdini Apprentice is FREE to learn Houdini with. Only downside is the Apprentice license can only generate apprentice files, so if you upgrade to escape or master later you can't use your apprentice files there.

Language & Networks (my simplified version)

 Everything starts off at the Object level/ Scene network. (You can tell by looking at the network view where you're at.)

OBJ - Objects, lives in Scene network, rig, light, camera and digital asset nodes or other networks can be held here
SOPs - Surface Operators, lives inside the Geometry network, mainly for modeling
POPs - Particle Operators, lives inside the Particle network, for particle effects
DOPs - Dynamic Operators, lives inside the Dynamic network, dynamic effects
ROPs - Render Operators, lives inside the Output network under "out", for setting up renders
COPs - Compositing Operators, lives inside the compositing network under "img"
CHOPs - Channel Operators, lives inside the Motion/Audio network, animation and sound manipulation
SHOPs - Shader Operators, lives inside the Shader network
VOPs - VEX Operators, lives in the VEX Builder network, for building custom procedures

You travel in and out of these networks through nodes (as seen in picture above, usually dop, pop, vop) or through the drop down list (which are global networks, usually shop and out). 

Expressions, Variables and Scripts

What makes Houdini procedural is it's methods of using expressions, variables and scripts to manipulate channels.  Channels can be referenced, evaluated and sometimes overridden by  other channels.  Learning these becomes very useful, but keep in mind Houdini uses Python and Hscript.  If there's an "H" on the top right hand corner of your parameters view you're using Hscript, click on it to change to python.  When in doubt, open up the Textport view and type in exhelp to get a list of commands, help on what they are used for, and how to use them in both languages.

Other helpful sites: Houdini Object Model Cookbook, Expression Cookbook, Global Variables