as lenient as you want to be - but keep in mind that the more "lenient" you are, the slower your results will be. also, you may not get the results you want at all if you're not taking in the right amount of protein, carbs, and fats.
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Goals: bench - 200; squat - 225; deadlift - 225
27/01/06: bench - 170; squat - 195 (wrapped); deadlift - 210; total - 575; need - 617; to go - 42
"Illegitimi non carborundum"
Make sure you have added strength training (3x per week) into that work-out regimine. Building muscles is the ONLY way to get toned. You cannot get great looking abs by just doing aerobics and diet, you need the muscle building factor as well.
3Norns is right, the more lax your diet is, the longer it will take to reach your goal.
Being lenient is a very relative term. You are an individual. One person's terms of lenient may be anther person's recipie for failure. It's all about trial and error and learning about what works best for your own system, then the most important factor, accepting it!
Nothing is static either. You don't get "tone" then your job is done. You have to maintain it or you'll lose it. The biggest problem is choosing a level of restriction in your diet that is unrealistic for your preferences or lifestyle. That's when you feel the need for leniencey. Just make sure you are not looking for an excuse not to do the "hard work", but then on the other hand you may be making a bigger deal out of restrictions than you really need to.
A lot depends on the point you are starting from and your expectations.