My wonderful wife gave me an Arduino startup kit from HVW for Christmas this year 
Best. Wife. Ever.
I've worked my way through all the examples and naturally started to wander from the beaten path (that's the point isn't it?). I built up a little 2-axis accel circuit on a proto board and replaced the example's LDR with one axis output without any drama. Both the Processing and Arduino sketches worked as expected (nothing to change in all fairness).
I then updated the Arduino sketch to read and output both axis values, one after the other. Using the serial window, I can see both axis values moving independently as I shift the proto board around.
I updated the Processing sketch to read for & output to the screen, the two variables however it's not operating correctly. I've no means to ensure that the data being assigned to the X axis or the Y axis is indeed x (or y) data from the Arduino. Beyond that, it would appear that the X axis is getting the bulk of the data - there's very little flutter when the board is idle and no response when the board is moved on the Y axis display, despite there being data from the Arduino.
I've searched for information on the Serial. library without finding anything and despite the multi-axis accel tutorials, they're only covering the Serial.println end of the equation and not the receiving end. As an utter and complete noob, I'm at a loss.
My gut instinct is to treat it much the same way the #xxxxxx is sent to and processed by the Arduino - append a designator to each channel's data, then extract it similarly on the processing side. What I'm not clear on is how to go about this. Trying to simply append "x" to the variable gives me the invalid conversion from 'constant char*' to int error. The tutorial on the 3-axis accel inserts a tab between the first two axis outputs and then a delay after the final one - but again, no examples on how to receive the data.
:-/