You will have been asked in advance to bring information about ALL of your debts, your latest statement or letter from the creditor will be enough. You might have court paperwork or bailiff information as well....the golden rule is just to bring everything together with details of your income.
The adviser will sort the debts into an order of importance and deal with any looming emergencies by contacting the creditor to ask for time to set things in motion. You will then work together on a preliminary financial statement. This is simple a budget sheet that shows your income on one side and your essential spending on the other. There are agreed amounts for housekeeping depending on family size and ages of children but don't be too worried if these appear low for you adjustments can be made. All payments to priority creditors will be included in this.
Spending is then deducted from income and if anything is left it will be shared out amongst the non-priority creditors. If there is zero income left then token offers of £1 per month will be made. The interest will be frozen. Creditors rarely disagree because if they went for court action, the courts work from the same figures as the advice agencies.