While the 28-year-old admitted that she couldn't dish out too many tips until she'd tied the knot herself, Lauren did have some pearls of wisdom to share.
"I have some advice just from being with my friends and experiencing their day with them," she told Allure magazine.
"I think it's important to look like yourself on the day. You don't want to be wearing so much makeup. And do a trial run so there are no surprises on the day. That would be a bummer!"
As the cover girl of the magazine's next issue — making it her third time — Lauren was sharing her tips in a behind-the-scenes video with the publication.
Speaking about general beauty advice, Lauren revealed her biggest fail in the makeup department.
"Trying to do way too much was my failure," she said. "I've learnt to pick one thing and go with it. If you have a simple outfit, you can have more fun with your makeup. But if you have statement hair, keep your makeup minimal.
"It's all a balancing act when you're putting your look together."
And when it comes to using products, Lauren admitted that at one point she had up to 20 cosmetics but it all boils down to using the few items that are good for you.
"At night, I trade off between a gentle cleanser and an exfoliant," she added. "And I use Egyptian Magic. I just put it all over my skin. It has olive oil, honey, all natural ingredients."
The fashion designer and author revealed her engagement to Will last October, by posting a photo online of her stunning cushion-cut diamond ring.
"I am very excited to share with you guys that William and I got engaged over the weekend," said the former The Hills star. "I am beyond thrilled!"