Firstly, what is involved? Basically you will deliver catalogs through letter boxes, go back a few days later and hopefully take an order, order the goods from your company and then go out again and deliver them. Sounds simple, eh?

Do you live in a town or city, or in a quiet, rural village? You need to have enough homes within easy reach in order to do well at catalog sales.
Are you situated close to an affluent area? If you live on a council run estate, or other poorer area, the residents may not be able to afford the products you are offering.
Is the area you are thinking of working available? You may be able to find this information out from the company but also ask neighbours if they get any catalogs delivered. You don't want to step on any toes!
If you can genuinely answer yes to all or the majority of these questions, then you might be able to make this enterprise successful.
There is however, one more question to ask yourself before you decide if there is extra income in catalog sales...
Can you afford the initial outlay? Most companies require you to purchase the catalogs and sample products before you start. If your endeavour does not work, can you afford to write off that investment?
If you are happy that you have enough potential customers and you fit the requirement then are you ready to make a start?
Yes, they need to be out there, working for you. You can't make any money if they are stored in a cupboard in your house!
You will need to put together some form of diary, in order to keep track of your catalogs. You may well have been provided with a "Round Robin" book, which has instructions on how to use it printed on the back. If nothing has been provided then you need to keep a record of the house number, when you left the catalog and when you have promised to pick it up again.
If you just drop the catalog through the door and walk off, the chances are that you will never see it again. The house owner will pick it up, put it down somewhere and forget all about it. When you go back to collect, they will not be able to find it, and often will not have even looked at it.
You are likely to get better results if you knock on the door when you deliver them. That way you can find out if the person is interested and arrange the best time to collect the catalog. If you are given a particular time, then make a note of it and turn up when you say you will. It helps to build trust with your potential customer.
If no-one is at home, and you still want to leave the catlog, then write a note to the householder asking them to leave it out at a certain time. If they do not do so, you will need to knock and ask if they have had a chance to look at it. If they haven't you may want to point out some special offers or items that you consider may be useful for them. If you can encourage them to look while you wait, then you may still get an order.
In this way you can build up a list of your best customers, and strike off those that are not worth pursuing.
Once you have received all your orders, you will need to place an order with the main company. This could well be before you have collected the payment from your customers. Some companies may allow you a certain "credit period" before you need to pay them. In other cases you will need to pay up front.
When the goods arrive, you will then need to sort them, so you know where they are to be delivered. Match up the paper order and the goods, and bag them if necessary.
Deliver when you said you would, unless an emergency prevents this. Keep your word, and your customers will appreciate it and learn to trust you. It is sensible to explain that you are not able to leave the goods if they customer does not pay for them. If you do, the chances of actually getting paid diminish, and you could end up out of pocket.
Your extra income in catalog sales is taken out of the money you collect, which should be more than you need to pay your supplier.
It is wise to keep an eye on the closure dates for these special promotions, and if necessary adjust the dates when you send in your qualifying orders. It is not a good idea to make up the quantity by buying products for yourself, whatever the temptation, as that can eat into your profits. Instead drop off extra catalogs within the time frame to give yourself the best chance of reaching your targets.
Your best chance of earning a significant extra income in catalog sales comes from recruiting others to do the same thing.
It is quite likely that you will be introduced to this system by somebody you know. Whoever it is always sleep on it, before making a decision.
Good luck, keep positive and remember you are not going to make an extra income from catalog sales unless they are out there working for you!