Egg laying

Hi All,  This may seem a very silly question & probably one which has been covered b4, bbuuuttt - how can you tell when a chook is likely to start laying - info from book says - wattle & comb firm up & turn bright red and chook will start 'prating'??!!? Being new to all this (sorry no piccies yet not sure how to post them here) we were told 10 days ago when we collected them that the leghorn (Missi - short for Mississippi) & the Rhode Rock (Dixie) were not far from laying but we're still waiting! Will we have to wait until ALL chooks have caught up with each other i.e. wattles & combs at similar stage?  OH is threatening to have VERY expensive roast chicken Sunday lunch next week - keep telling him 'patience'.

Thank you Sarah, will try & get some piccies on here soon!