To give a tutorial on percentages, you want to start with the idea that "percent" means "per 100." Start with a few examples such as 1 out of 100 = 1%, and 50 out of 100 = 50%.
You can establish this concept using a 10x10 grid. Have your grid on transparency and shade in portions of the grid (such as one square) and have the student state what percentage is shaded. You should then alter the base number in your example. Have only one row of your grid, or 10 boxes, visible, and shade in only one box. Be sure the student can appreciate that this is now 10% of the whole row.
From here you want to move on to expressing percentages as a decimal and fraction. To convert to a decimal, use the trick where you place the decimal two spots to the left of the last number in the percentage. If there are any spaces, tell the student to put a zero. Thus 50% becomes 0.50 and 5% becomes 0.05.
To convert to a fraction, have the student put the percentage over 100. Then, if the situation calls for it, have them reduce the fraction. Thus 50% becomes 50/100 and 5% becomes 5/100, or they can reduce this to 1/2 and 1/20. If they are struggling with reducing, remind them that they need to divide the numerator and denominator by the same number.