Important
Visual observing of satellites
You can easily observe satellites flying above your head with naked eye, if three conditions are fulfil:
satellite is illuminated by the Sun (it isn't in Earth eclipse; light color on screen),
its close enough and has brightness in visible range,
sky is dark enough and clear.
The most visible satellite (excluding Iridium flares) is ISS (even mag -1.5). Other satellites, you can catch with naked eye, are grouped in VISUAL.TXT TLE file.
Updating TLE files
For accuracy of prediction your TLE files must be up-to-date, download this data are available for example on www.celestrak.com or www.stoff.pl. You can use TLE Updater, implemended in Orbitron Setup to preform this operation.
It's difficult to determine maximum TLE age for perfect prediction. For satellites like ISS, you should update TLE every few days. For Iridiums one month updating is enough. NOTE: After each satellite manoeuvre, TLE data lose it's validity. It's important for ISS, after shuttle docking or manoeuvring new satellites. If you have Internet connection, just update your TLE files every day.
Time
You need perfect time information. Your watch should be synchronized with professional clock. You can set it using model signal emited at noon by national radiostations (in Poland - 1st Program of Polish Radio). In Orbitron 1.3 and above there is an Internet time synchronization via NTP, try it in Setup. For naked eye observation few second precision is enought, for flares observation 1 second precision is nice, but when you use telescope your watch should be synchronized in tenths/hundredths parts of second.
Your coordinates
Your city coordinates (longitude/latitude) should be also exact for high precision prediction. To find them, you can use GPS, maps or check it on www.heavens-above.com