The first thing you want to figure out is the size of the table. It is advisable to plan the size in pixels, even though percentages are allowed. Using pixels ensures that the table will look how you want across browser platforms and screen sizes. The width is the dimension you most need, however knowing the height makes it even easier.
The next thing you want to decide on is the layout of the table. In other words, how many rows and how many columns do you want? The possibilities are virtually endless, although any table with more than four or five columns can sometimes become too cluttered.
Thirdly, you want to give each row and each column corresponding dimensions. If you set the width and height of the overall table, you want to make sure that the width of the columns adds up to the overall width of the table and that the overall height of the rows adds up to the overall height of the table.