More people are learning about and getting into the LEGO investment market everyday. It can take a lot of patient trial-and-error to build a successful LEGO “portfolio.” Even people who have been in the market for a long time struggle to maximize their profits due to some common, but very correctable, errors.

Here are 11 of the most typical mistakes LEGO investors – buyers and sellers – make. Addressing them can make a real difference to your investment success.

1. Misjudging Relevancy

Predicting how certain LEGO sets are going to perform in the investment market can be difficult. Sometimes buyers select sets they believe are going to be retired sooner than they actually are, leaving them with multiple quantities of sets with a longer shelf life.

Alternately, LEGO investors may not stock up with enough short-term sets that they can turnaround for higher profits more quickly.

2. Not Keeping Up on the Latest LEGO News

LEGO is one of the most written-about toy brands in the media. New releases get a lot of pre-sale coverage, and the collectibles market commands its share of ink as well. Simply setting up a Google Alert for LEGO-related news is an easy way to stay on top of activity in the marketplace, but it’s a step many LEGO investors fail to take.

Several news sites publish entire lists of LEGO sets that are retiring soon. These news sources are especially helpful when you’re developing your investment strategy. Looking out for upcoming new versions of retired sets is also important, as the revived sets can impact the value of the original, retired ones.

3. Overlooking Non-Franchise Sets

Star Wars, Harry Potter, Marvel Avengers, and Disney Princess sets are, and likely will always be, perennial favorites of fans and collectors. But some of the sets that rake in the highest selling prices are internal LEGO brands, like the Creator Expert and Factory series.

Sets like Café Corner, Market Street, and Grand Carousel consistently rank in the upper reaches of the most valuable LEGO sets around, selling for several times their original retail value.

4. Selling Too Early

Timing the marketplace is an essential skill to develop in maximizing your profits from LEGO sets. Some LEGO investors put recently retired sets up for sale too soon, before their value has had enough time to appreciate. It’s best to wait a while to gauge the market reaction and price movement.

5. Not Being Candid About Set Conditions

When selling LEGO sets, it’s always best to be forthcoming about condition and contents. Buyers don’t like to be surprised by sets with missing pieces or defects. Be entirely honest with your product description, from shipping weight and prices to quality and set integrity.

6. Miscalculating Shipping Costs and Seller Fees

Shipping rates and incidental fees can be the undoing of profit margin for LEGO investors. Underestimating shipping weight is one of the more common, simple mistakes that resellers commit. Failing to account for online seller fees is another — eBay charges a commission cut for every transaction on their site.

There are a few preventative steps LEGO investors can take to cut back on shipping costs, like buying postage in advance online and opening a business account with major carriers like UPS and FedEx.

If eBay commission fees are cutting into your profits too much, you can consider more off-the-grid selling sites that don’t charge fees, like Craigslist (although you’ll have to weigh those sites’ relative lack of security).

7. Pricing Sets Too High

Even if you have a set that’s a surefire target for collectors, they may balk at the asking price if it’s too high. That’s why it’s always important to compare the prices other sellers are offering for similar LEGO sets. If yours is too expensive, buyers will keep looking for a better deal.

Some LEGO investors overlook the quality or condition of the sets they sell, thinking that the rarity of a given set alone infers its value, and they can price it highly just for that reason. But collectors care deeply about product conditions and missing pieces. Those factors have to be considered along with the set’s market demand.

8. Buying Too Early

Again, it’s hard to predict what sets are going to break through to the collectibles market. Some buyers pick up multiple quantities of new sets believing they’re guaranteed hits.

But not every new set is bound to pop, no matter how recognizable the connected franchise or brand may be (The Simpsons set was a notorious disappointment, sales-wise).

Much like a stock investor waiting to buy shares until after a company’s IPO, it’s not a bad idea to hold off on buying new sets until you see how well they perform in their first weeks of release.

9. Not Buying from Physical Retailers

Obviously, most commercial transactions of LEGO sets happen online these days. You’ll never not use sites like Amazon to pick up sets. But few of the biggest eCommerce sites offer sale prices, while many brick-and-mortar outlets do. Pay a personal visit to these stores to find potential bargains you won’t get online.

10. Underestimating Value Opportunities

It’s always tempting to stock up on LEGO sets once they go on sale, sparking a rush to the cashier. But focusing on the most popular sets may cause you to overlook exclusive sets or sets that were never offered to the general public. These incredible value opportunities are often lost in the mass-consumption fray.

On the other hand, some LEGO investors load up on smaller LEGO sets to the exclusion of bigger ones. Larger sets are always more in demand on the resale market, so buyers who intend to resell sets for profit should stick to the big sets.

11. Failing to Research

It’s crucial to vet LEGO resellers before you buy. Always check the vendor’s star ratings and customer reviews to verify if prior buyers were satisfied with their transactions. Also, LEGO investors should get as much quality information as they can when buying LEGO pieces in bulk. Investors are often disappointed with bulk pieces that became dirty or grubby after sitting in a bin.