The holidays are an ideal time to rack up an abundance of frequent flier miles and hotel loyalty points, but not necessarily from all your trips back home. While traveling is still the best way to redeem your loyalty rewards, it's become one of the least efficient ways to earn them. The trick is to use online shopping portals — especially now, when gift-giving season is in full swing. Using portals is free, and can be done with minimal inconvenience, meaning you can score additional points and miles with just a few extra clicks. See: 5 Ways to Earn Miles Without FlyingAlmost every airline in the United States, and a number of hotel chains, have created their own shopping portal, such as American's AAdvantage eShopping mall, Marriott's ShopMyWay or even Amtrak Guest Rewards Points for Shopping. Banks have portals as well, but you usually have to hold a credit card at that bank to use its portal. Shopping portals partner with select retailers, many of which are mainstream stores you've undoubtedly shopped at before like JCPenney, Staples and Walmart, to name a few. These merchants, which usually number in the hundreds, have agreed to award extra loyalty points to any member who uses the shopping portal to buy goods at their website. You get extra miles or points, while retailers enjoy extra traffic. For instance, a store like Macy's might offer 3 extra miles per dollar spent at macys.com to members of the shopping portal. Depending on the retailer, these bonus miles can get incredibly generous, even as high as 30 points or miles per dollar. So when you sit down at your computer to do your online holiday shopping, your first step should be to sign into a shopping portal. On the portal home page, you'll find a list of featured merchants and a search function to find others. All these merchants are offering extra miles for purchases, so if you find a portal merchant that sells what you're looking for, it's just a matter of clicking on that merchant at the portal first. That click takes you to the retailer's normal website, which looks just like it would if you navigated there directly. From there, you can buy your items as you normally would, but the portal will automatically track your purchase and award extra miles based on the amount you spend.Each portal has agreements with different merchants, so you won't always find the same merchants on every portal. Also, the number of extra miles offered by any given retailer fluctuates over time, sometimes daily. Even two portals with the same merchant might offer different mile-per-dollar amounts. So with all the payouts changing daily, how can you keep track of which portal offers the best return at any given store? A number of "portal finder" sites, such as CashbackHolic.com, Cashback Monitor and evreward.com, can assist with that task. Not only do these sites track the ongoing payouts from travel-based shopping portals, but they also report on cash-back portals like ShopDiscover and Upromise. These types of sites can also be an excellent way to find lists of all the available shopping portals. And since it's completely free to join a shopping portal, there's no reason not to sign up for all of them.And remember: For airline and hotel shopping portals, you're not required to pay for your purchases with a co-branded credit card. That means you can easily go through a portal like Delta SkyMiles Shopping, charge your purchases to any credit card, and still get extra SkyMiles on top of your usual credit card rewards.See: Are Frequent Flier Programs a Fool's Game?The incentive for shopping with a portal right now is twofold. Since you're spending more, you're also earning more. And since shopping portals routinely offer limited-time holiday bonuses, you have the chance to reap even more rewards.For example, in recent weeks the Southwest Rapid Rewards Shopping portal offered an extra 300 Rapid Rewards points for every $175 spent at its portal. This was in addition to the extra miles offered by each merchant.Sometimes these holiday bonuses are targeted specifically to existing portal members, so when you sign up for a portal, remember to opt in for e-mails so you're in the know about the best bonus offers. If you're shopping offline, using an online portal would seem to be out of the question. However, there are two tricks you can use to get bonuses even when you want to get your items in store.One alternative is to do your shopping online and select in-store pick-up at the end of the transaction — an option that a substantial number of brick-and-mortar stores offer. For instance, if you wanted to buy items at a Target store near you, you could use a shopping portal to go to Target.com, choose your items, select in-store pick-up at checkout, and then get in the car and head over to Target to retrieve your purchase.When it's necessary to actually be in the store while shopping, such as when you might want to try on clothes, there's a trick for that, too. In this case, you need to find a retailer that allows shopping portal points to be earned on the purchase of store gift cards like Sears, for example.Most portals specifically state they are eligible for rewards on the purchase of Sears gift cards. So if you wanted to buy $200 worth of clothes at Sears, you could go through a shopping portal to Sears.com, buy a $200 Sears gift card, and then use that gift card at a Sears store to pay for your purchases.But remember: By using a gift card instead of a credit card, you're forfeiting any extended warranty offered by banks on credit card purchases. While that won't make a difference for clothing purchases, it might not be worth risking for major appliances.Shopping portals are a fantastic way to accumulate travel points and an important tool for any loyalty program junkie. Before you set out on your holiday shopping this year, consider starting at a shopping portal. See: Best Travel Rewards Programs of 2014-15About the author: Julian Mark Kheel learned the ins and outs of travel loyalty programs while flying more than 200,000 miles a year as a TV producer and director. He takes a contrarian view on travel wisdom in his "Devil's Advocate" series every Thursday at the blog Travel Codex. You can also reach him on Twitter @dvlsadvcate.