In preparation for the full Arecibo Legacy Fast ALFA (ALFALFA) extragalactic HI survey, precursor observations were carried out in 2004 August-September with the seven-beam Arecibo L-band Feed Array (ALFA) receiver system and the Wideband Arecibo Pulsar Processor spectral processors. While these observations were geared mainly at testing and debugging survey strategy, hardware, and software, approximately 48hr of telescope time yielded science-quality data. To test our ability to discriminate cosmic signals from radio-frequency interference and noise, 165 candidates ranging in reliability likelihood were reobserved with the single-beam L-band wide system at Arecibo in 2005 January-February. Of those, 41% were confirmed as real. We present the results of both the ALFA and the single-beam observations for the sample of 166 confirmed HI sources, as well as our assessment of their optical counterparts.