A bit more about weighing
First, if you don't want to be on the spreadsheet, you don't have to be.
Second, if you are on the spreadsheet, you don't have to declare your actual weight if you don't want to. Instead, you can index it - so your starting weight is 100. Then you take away one for every pound that you lose.
Frequency of weighing
This is entirely up to you. Some of us find that daily weighing is what keeps us focus and ensures we stick to the plan. However, if you're doing to do this, you have to accept the fact that your weight will fluctuate on a daily basis, and it's not uncommon to see the scales go up, even when you know you've been following the rules to the letter. For some people, this is too difficult psychologically, and can lead to a serious case of the fuckits, where they go massively off piste as a result.
Don't do that! If you can't cope with this, then go for weekly weighing instead. As I post the new chat thread each week on a Monday, it makes sense to make that your weighing day - but it doesn't have to be. You can choose whatever day of the week suits you best.
What weight to enter?
If you're a weekly weigher this is simple 
But if you're a daily weigher, then you have different options:
- the weight you see on the scales on weigh-in day
or
- the lowest weight you've seen that week
or
- an average of all the readings for the week
When to weigh
First thing in the morning, naked, after you've been to the loo. There's no point in weighing later in the day, as all you're doing is weighing yourself plus your clothes plus anything you've eaten and/or drunk.