Some things that you should do to better your score in XAT :
Practice. Practice makes you perfect, practice makes you confident. 1 month before XAT, I had already taken around 50 odd mocks for CAT, 1 live CAT, 8-10 mocks of various other exams like IIFT, SNAP and 2 live exams for SIBM and IIFT.
The month before XAT was spent in solving more mocks, revising mistakes and important points in the 50 old mocks. IMS mock XAT test pack (The papers are balanced and on the lines of current XAT papers) along with mocks from CL were useful in this regard.
Remember, a mock is never useful until it's analyzed properly after you take it. Analysis should ideally take 3 hours or so. Mark the questions you feel need revision, mark the kind of questions you see often in different mocks so that they can be revised quickly later.
Solve as many previous years XAT papers as you can. Most of them are provided by your coaching institute/online prep sites.
In DM questions, one has to be ethical even if sometimes it's against monetary interests of the person/business. Be balanced when it somes to poor and rich. No external factors should come into play when you're making a decision.
Try to get your hands on CL XAT supplement, CL DM supplement.
For VA in particular, CL and IMS mock papers along with GMAT Manhattan VA supplements did the trick for me. Read a lot, especially the 'boring' ET editorials and Hindu editorials. Eventually, you will develop interest in them and start loving them. Reading such articles will also help you deal with an RC passage from an area outside your comfort zone.
In the paper, remember, never do guesswork. (Especially in DM since it's very tempting). Only answer the questions you are sure of and you have more chances of cracking the exam.
Give equal importance to all sections. Something I did and it may or may not be useful to you : Try to solve each section in 2 rounds. 1st quick round for solving all the easy questions and questions from your fav topics. 2nd one to try the moderate ones. Don't even touch the tough ones until you've solved all 3 sections using the 2 round method.
Start talking and thinking in english. It'll go a long way in helping you tackle the VA section and in your interviews.
Believe in yourself. Even if you are weak in say, quants, think you aren't & that you love the subject and slowly but surely, you'll start solving more questions in mocks and become better at it. (Ofcourse it'll involve practicing quant but you don't mind it since you 'love' it )
Lastly, very important to have a motivation. (For most of you/us, it is the glorious XLRI ).