just put a price at whatever you are willing to pay for it and walk away. if you get it, great, if not, then you may want to consider increase your price.
you can also buy in chunks. say, you want a total of 1,000 shares, buy in increments of 250/shares, 4 times. this way you "cost-average" your shares. makes sense?
i have been watching scln for over a weeek now and accumulating for the past few days. today's close at $5.70 is very bullish and i'm looking for a $5.78 breakthrough. if this happens, scln can easily go back to the $6.00's.