How to Crate Train a Small Dog
To crate train a small dog, start by keeping the crate door open so your dog can explore and get used to it at its own pace. If your dog is reluctant to explore the crate, put some treats near the entrance or toss some inside and encourage it using a soothing voice. Once your dog becomes comfortable enough to enter the crate, start feeding it in the crate to create positive associations for your dog. At some point, you should begin closing the door while your dog eats, and gradually increase the time it spends in there before you let it out.
Purchase a crate. Plastic crates are generally more appropriately-sized for your small dog than larger, metal crates; dogs under 38 lbs. should have crates sized 24" by 24" or smaller. Successful crate training requires that your dog instinctively avoid soiling its sleeping area; the crate should not be big enough for your dog to use one end as a bathroom. Make sure the crate is large enough for your small dog to stand up straight, turn around, and lie down comfortably. Make the crate comfortable. The psychology of crate training works with a dog's instinctive desire to have a warm, safe place to sleep. Make your pet comfortable in their crate by placing a soft bed or blankets inside of it. If your small dog is not housebroken, line the crate with thick, comfortable towels that can be easily removed and washed. Keep the crate nearby. Put the crate in a central location in your house where your dog will be able to see what is going on around it. It is important for your dog to have positive associations with its crate and see it as a refuge, rather than a source of isolation. While dogs may enjoy their den-like retreat, they are largely energetic and social animals who require mental stimulation and companionship. Let the dog explore. Take the door off of the crate (or prop open the door, if this isn't possible) and allow the dog to explore it freely. If your dog does not approach the crate on its own, try encouraging it in a soothing voice. Drop treats near the entrance to the crate, or toss treats and toys inside to encourage your dog to go in. Be patient and allow your pet to explore at its own pace. Feed your dog in the crate. If your dog is comfortable enough to enter the crate, begin feeding it regular meals in there to increase positive associations. Place your dog's food dish towards the back of the crate; if your dog has not fully explored the crate yet, place its dish near the front instead. Do this a few times, then close the door while your small dog eats; open the door as soon as it finishes its meal. If the dog cries or whines, shorten this time period and open the door sooner; if your dog seems comfortable, prolong the time to ten minutes after it finishes eating. Attempt longer crating periods. If your dog gets comfortable with the process of eating in its crate, start practicing longer crating periods. Draw it towards the crate with a treat and soothing words; encourage it to enter, then close the door behind it and feed it the treat, offering lots of praise. Sit by the crate for 5-10 minutes, then leave the room and wait another few minutes before returning to let your dog out. Repeat this process several times a day, increasing crating time gradually. Leave the house. If your small dog can stay in its crate for 30 minutes without getting anxious or scared, try leaving it crated while you leave the house for a short period of time. Crate the dog between 5-20 minutes before you step out, and try to be discreet about getting ready to go. Keep your departure and arrival home easy going to avoid making your dog hyper. Continue the process of crating your dog while you are home as well to prevent associations of loneliness or abandonment with the crate. Crate your dog at night. Start nighttime crating with the crate in your bedroom; this way, you can let your small dog out if it whines to go to the bathroom. Lead the dog into the crate with praise and a treat, as already established, and close the door. Once your dog is comfortable spending the night in its crate, you can move it to a better location, or choose to keep your pet near you. It may be difficult to distinguish whether your dog is whining because it needs to relieve itself, or because it wants to be let out. In the case of the latter, avoid reacting negatively or positively; letting your dog out (for any reason other than to eliminate) will encourage it to whine in the future. Prepare for company. If you are expecting guests who are uncomfortable around your dog, put your dog in its crate before they arrive. If this is not the case, simply have the crate ready in the event that your dog gets overexcited – if this happens, calmly bring it to its crate, and place treats and toys inside to make things more comfortable. Note that this should not be a punishment – dogs pick up on the behavior of people around them, so even well-behaved dogs can become rambunctious around a lively group of guests. Bringing your dog to its den is simply allowing it the opportunity to calm down and prevent problem behaviours. Travel with the crate. Crate training is important in preparing your dog to be transported, which will occur at various junctures in its life (e.g. trips to the veterinarian's office). Make a point of taking practice trips with your dog in its crate; this will ensure that your dog doesn't associate being transported with events that may cause it stress, exclusively. Dogs who have never been crated are more likely to be anxious during such trips and uncomfortable being confined. Take your dog outside as soon as you let it out of the crate. To discourage your dog from relieving itself in its crate, try to take it out to eliminate as soon as possible after long crating periods. This will build your small dog's confidence that its needs will be met if it cooperates. This should not be difficult, as dogs have as a natural instinct a reluctance to soil their sleeping area. Keep the crate. If your dog has developed an affinity for its crate during training, consider keeping it as a fixture in the house. Remove the door and place it in a more discrete area, if preferable. Given the size of your small dog's plastic crate, it can be moved easily from one room to the next, and used as a carrier for car rides. Seek help if needed. If you have exhausted all efforts in trying to crate train your dog, reach out to a professional for help. Search online for listings of dog trainers in your area; visit the Association of Professional Dog Trainers (APDT) website to search for trainers by zip code. Be sure to ask potential trainers about their credentials, methods, and services before you hire them, and don't hesitate to ask for references. Some key questions to pose to them are: ”What are your credentials?” ”What services do you offer?” ”Do you assist owners with crate training?” ”Do you have a list of clients I can contact for references?” 
Purchase a crate. Make the crate comfortable. Keep the crate nearby. Let the dog explore. Feed your dog in the crate. Attempt longer crating periods. Leave the house. Crate your dog at night. Prepare for company. Travel with the crate. Take your dog outside as soon as you let it out of the crate. Keep the crate. Seek help if needed. 