I think the foremost thing to do before entering Sikhi is to understand what you are getting into. Knowledge is power. If the foundation of one's Sikhi is knowledge and solid understanding of Sikhi, then nothing can shake one's Sikhi but if one gets into Sikhi following some person one admires, then one's Sikhi will be just as strong as that person's Sikhi is. For this reason, it is important to read some books on Sikh theology.
There is a saying in Punjabi that when one goes to buy even a simple clay pot, one examines it carefully; then how can one adopt a spiritual way of life, without first understanding it. I would strongly recommend Bhai Sahib Randhir Singh jee's Jail Chithiaan or its English translation as the beginning. This book will teach one about Sikh's way of life and what the ultimate aim of a Sikh is.
Once one is clear on what one is getting into, the next thing would be to practically do it. Starting to read baani is something one should do early one. Siri Jap jee Sahib is of course the first Baani one should start reading. One should practice wearing the 5 Kakaars but before that one should give up intoxications and start eating vegetarian. Try sleeping early and getting up early. This way get a feel of what Sikhi is.
Ultimately, one's real journey begins only when one takes Amrit and start Japping Naam. The most difficult rehits and standards of Sikhi become easy after japping Naam. This daas did paath of 5 Baanis for the first time only after taking Amrit. Before that I had never read even Siri Jap jee Sahib. Amrit has such power that it does not allow one to falter. It is very strong.
Good luck to you and welcome to Sikhi!
Kulbir Singh
ਸਤਿਗੁਰਬਚਨਕਮਾਵਣੇਸਚਾਏਹੁਵੀਚਾਰੁ॥