1. Deadlift More!
If you ask the average gym enthusiast, they will say that the Deadlift is a simple movement--- bend down, grab the bar and lift. But, contrary to that belief, the Deadlift is a technical, full body movement that requires the ability to properly hip hinge, stay tight through the entire movement, as well as have the mobility to actually get into the proper starting position and maintain that form through the whole lift.
The Deadlift is typically an exercise that most people push to the side and only use when they want to max out on it--- this is not an optimal way to train the lift. In order to add real poundages onto the bar, you must train the Deadlift with different ranges of volume, intensities, as well as FREQUENCY.
If you're currently only Deadlifting once a week, try adding in a second Deadlift day that includes a lighter variation, such as the Stiff-legged Deadlift or Romanian Deadlift. This will allow you to train the Deadlift with more frequency without overtaxing yourself or compromising your Max Recoverable Volume (MRV)--- and it will also allow you more time to practice the Deadlift movement itself.
2. Deficit Deadlifts
In my opinion, Deficit Deadlifts are one of the best variations for overall strength and to improve your regular Deadlift. The Deficit Deadlift increases the range of motion---therefore making the lift harder. But, the Deficit Deadlift also teaches you to stay tight at the bottom portion of the lift, which is crucial for breaking the bar off the ground and also maintaining a tight, flat back.
There are countless benefits to using this variation, but there are also many factors to consider. If you have poor mobility and cannot get into a proper starting position, then the Deficit Deadlift is not for you.....yet. Improve your mobility first, then feel free to incorporate them into your training. Also, one of the things that are far too common is when people use a huge deficit. In order for the Deficit Deadlift to be effective, you only need to use a 1"-2" deficit--- using any more than that could put you at potential risk for injury, and the benefits do not increase with the larger deficit.
Mobility is one of the most important and most overlooked factors to consider when improving your Deadlift. If you are not sufficiently mobile in the hamstrings, as well as the thoracic spine, then you will be unable to get into a proper starting position to pull.
By performing daily hamstring stretches, along with dynamic stretching (such as leg swings) and performing single leg RDL's (hip hinge movements) with full muscle contraction, you will be building the proper mobility to add weight to the Deadlift--- and you will also be protecting yourself before you wreck yourself. Check out Jonnie Canditos hamstring mobility video HERE