By Tom Barlow, dealnews contributor According to the Wall Street Journal, the trade-in value for most used cars is currently at an all-time high — with several models increasing in value since last year — making this the perfect time to consider selling. But according to Philip Reed, Senior Consumer Advice Editor for Edmunds.com, you can still squeeze even more out of your car with just a little care and attention. Reed says that the secret to getting the maximum trade-in price for a used car is returning it to pristine condition, inside and out, with detailing. "It could make a difference of 2.5% to 5% on the sale price," Reed says. He also points out that having your car detailed is a great way to hold the line on your original asking price. But more importantly, since the market is all about curb appeal and that important first impression, detailing "could be the difference between selling and not selling" at all, Reed says. Don't lose a sale or that extra 5% ($500 for a model that's estimated to sell for $10,000) by offering up a car that's smelly, scratched, or filthy. A small investment in supplies and a single afternoon of detailing, following the steps below, could increase your car's selling price by hundreds of dollars. Starting on the Inside It's easier to clean a car from the inside out, so begin with the interior. Vacuum it thoroughly (most car washes have vacuums if you don't have one at home), use carpet spot remover on stains, and lift any pet hair with a loop of masking tape. Or, if necessary, shampoo the seats just like you would your indoor carpeting. If you have leather seats, instead use a special cleaner and conditioner (see the suggested supply list below for all product references); nothing makes a car look older than cracked, stained leather. The vinyl or plastic parts of the dash, door, and between-seat console can be cleaned with a weak soapy water solution, made with the suggested automotive soap. Then, use the quick detailing spray on a cloth dipped in clear water to remove streaks. Dust hard-to-reach spots and crevices with either a Q-Tip or a credit card wrapped with a thin cloth. Finish by thoroughly cleaning the windows and mirrors with an ammonia and water solution, or a commercial product like Windex. However, if your windows are tinted, look for an ammonia-free cleaner, as the product used to darken windows is often reactive with ammonia. Lastly, open each door and clean the jamb. At the Car Wash Before cleaning the outside of the car, remember this one rule: If any rag, mitt, clay, or chamois falls to the ground, immediately put it aside. Otherwise, there's a good chance you'll be grinding road grit into the finish. Begin cleaning the exterior by parking the car in a shady spot and rinsing it thoroughly with a hose. Apply bug or tar remover anywhere that this goop has built-up, then spray wheel cleaner on the wheels. Allow both substances several minutes to soak in to the affected areas. To wash the car, use a two-bucket system. The first bucket has the water and automotive soap solution, while the second has clear water. Use a nylon-wrapped sponge (which gives the sponge some scrubbing power) or a washing mitt for the soap bucket, and a separate sponge, mitt, or towel for the rinse bucket. Wash a section at a time, using back and forth and up and down motions; don't swirl, as this will grind grit into your finish. Then rinse each section with the clear-water mitt. Since the wheels will be the dirtiest, save washing them for last. A nylon bristle brush can help tackle that difficult combination of road grit and brake shoe dust. When finished, rinse the entire car with the hose again, then dry thoroughly with microfiber towels or a chamois. The Nitty Gritty Now that the grime has been removed from your paint, it's time to inspect it. Are there rough areas, where the paint has bonded with air-born particulates or chemicals? If so, you'll need a clay bar kit. Wet the rough area with the included lubricating spray, then take the bar of clay and cut it into thirds; you only need to use a third at a time. Knead this clay into a thin disk, and use it to polish the area in question. Again, use back and forth and up and down motions, and go gently — there's no need to smash the clay into the finish. You'll know you're done once your fingertips no longer detect a rough spot. Wash, rinse, and dry each area that you clay. Some minute scratches will polish out, but you can attack more substantial ones with a scratch repair kit. Once you've smoothed rough areas and fixed scratches, it's time to polish. Using a clean microfiber rag, spread a car polish on a section of your vehicle. (I like to do it in five parts: hood and left fender, left-side doors, back and right-side rear door, right-side front door and fender, and top.) Allow it to dry briefly, then buff with gentle strokes from a clean microfiber towel. When done, be sure to clean the polish off the areas where panels meet. (A paper towel-wrapped credit card comes in handy once again.) Next, it's time to attack the black rubber and plastic parts of your exterior. Going over them with a black-trim restorer product will bring back their show-room gleam. Use the quick detailing spray to add shine to any chrome parts and your wheels. Using a wax applicator, apply a film of wax to all of the painted areas of your car, a section at a time. Allow it to dry, then buff with a clean microfiber towel. Lastly, clean your windows one last time. Take care not to overspray onto areas already detailed. Drive your car out into the sun to inspect it for areas you might have missed. The final step? Sit inside and give your car a whiff. If it doesn't smell perfectly clean, invest in an under-seat air freshener. (The "new car" scent is obviously a wise option.) Add a "For Sale" sign to the window for good measure, and prepare for the hungry potential buyers to roll in. The Shopping List: Automotive soap, like Meguiars Deep Crystal Car Wash 64-oz. Jug for $4.74 with $5.29 for shipping at Ace Hardware Outlet via Amazon Microfiber towels, like this 12x24" Microfiber Car Towel for $1.99 each with free shipping at Meritline (rags from home are OK, as long as they're clean and soft). Wash mitt, like the Multifunctional Microfiber Car Wash Mitt for $3.99 with free shipping at Meritline. Black-trim restorer, like the Mothers Back-to-Black 8-oz. Bottle for $7.74 with free shipping via Prime at Amazon. Wheel cleaner spray, like the 3M Wheel and Tire Cleaner $9.96 with free shipping via Prime at TCP Global via Amazon. Scratch repair kit, like the Turtle Wax Premium Scratch Repair Kit for $16.99 with free shipping via Prime at Amazon. Spray-on detailer, like the Turtle Wax ICE Synthetic Spray Detailer 23-oz. Bottle for $7.09 with in-store pickup at Advance Auto Parts. Car polish, like the Nu Finish Liquid Car Polish for $8.29 with free shipping via Prime at Amazon. Car wax, like the Turtle Wax T-412R Ultra Gloss Liquid Wax 16-oz. Bottle for $12.03 with free shipping via Prime at Amazon. Wax applicators, like the Smartwax Large Microfiber Wax and Dressing Applicator 2-Pack for $6.76 with free shipping via Prime at Amazon. Clay bar kit, like the Meguiar's Smooth Surface Clay Kit for $15.94 with free shipping via Prime at Amazon. Leather treatment, like the Leather CPR Cleaner & Conditioner 18-oz. Bottle for $16.13 with $4.96 for shipping from Ozbo via Amazon. Tar and bug remover, like the Stoner Tarminator 10-oz. can for $9.61 with free shipping via Prime at Amazon. Total spent: $131 Check the National Automobile Dealers Association website to get an estimate on what your car should fetch on the market. Photo credit: hugo90 via Flickr Tom Barlow formerly wrote for AOL's WalletPop and DailyFinance, and in addition to his dealnews contributions, he currently writes about lifestyle topics for Forbes.com. You can follow him on twitter at @tombarlow. You can also sign up for an e-mail alert for all dealnews features.