What sensors are giving you trouble? DHT22?
I found with the DHT22 that doing the following helps in getting good and steady values:
Wiring => 10k resistor between Vcc and data line (try to twist the wires, connected to the sensor)
Initialization => I found that during initial readings, the sensor tends to do some weird stuff. I do 2-3 readings (in a loop) without using the resulting values during.
Timing => Reading the sensors to frequently gave me horrible results. Reading every 2 seconds works like a charm.
Hope it helps!