A consultant on his/her first project must:
1. Be comfortable with basic Excel formulas (in particular, sum-if/count-if and vlookup/index-match) and use Excel keyboard shortcuts;
2. Know where all the buttons in PPT are located and use PPT keyboard shortcuts (in particular, for aligning objects);
3. Know all the basic business notions/values (IRR, NPV, EBITDA);
4. Have read the Pyramid principle of communication by Barbara Minto book and internalised it;
5. Be comfortable performing mental math in his/her head: in particular, percentage calculations (multiplication).
Plus, if you are aiming to join a specific practice, such as Healthcare, Oil & Gas, Consumer, Fashion, etc. - you certainly must be familiar with the industry trends and key concepts.
I've actually made a video covering this topic - with specific tips - over on my nascent YouTube channel. The channel is called Angelina's Business World and the video in question is 5 Skills you need to survive your first year in consulting.
Hope this helps and Good luck!