I dont think of those things as rules so much as just etiquette. Not really a sin to not do them, if you forget or don't know.  

Seven things to do on entering Islam (By Yusuf Estes):

One- The most imp thing in the beginning is to focus on who is Allah? What is Tawheed (monotheism)? And how he is unique in every aspect and this to prepare ourselves for the test that is coming up.

Two- To be ready for the test that is for sure coming up if it hasn't already started.

You will be tested in every way u can imagine and a few that you can't imagine, and this is a part of the whole scheme in coming to Islam.
Allah said in (29:2-3):"" Do men think that they will be left alone on saying, We believe, and that they will not Be tested?

We did test those before them, and Allah will certainly know those who are true from those who are false.""

The word used In Quran is "Fitnah" which is more than a test. It has more deep meaning like a trial or being in difficulties, so be ready.

Three-Watch out from Muslims, this may sound weird but the biggest problem that most of us have when we entering into Islam are other Muslims.

Some will try to make everything is so easy for themselves especially, that they will take out important part of Islam and say they only try to make it easy for new Muslims.

Other is so strict that you will feel that u are in a box or in a prison and can't get out

Still others may mistreat and you can't understand what is going on with them and how can all this be

Four- Take every thing in Islam one step at a time and don’t back up from whatever you know

Now this is very essential point upon Islam. Something are small but done on regular basis is most beloved to Allah than something that is big but only done once or twice

So regularity and consistency is the key here.

Five-The Halal and Haram, this is what is permissible and what is forbidden.
This 2 Arabic words can makes you crazy if you don’t find the balance really quickly.

Many arguments occur these days between Muslims themselves over the issue of what is permissible and what is forbidden in Islam and most of the time there is lake of knowledge and understanding regarding these topics ,so it is better not to get into these discussion with people without first having a deep knowledge and background on these matters

It is your right even your duty establish the evidences for what people telling you concerning the matter of what is permissible and forbidden in Islam.

This is not to be taken lightly nor should we be quick to pass information to others without being sure from this information.

When brothers and sisters send you Emails to talk with you regarding subject that fall in this category we recommend that you investigate their proves and evidences before you accept or reject what they are saying and especially before you pass this info to somebody else because when you start to passing information to others whether in the masjed, street, over the telephone or on the internet, this could be a problem. Don't forward Emails on these subjects regardless what the emails tells you to do or reward you are going to get UNTILL you have probably established the evidences for the subject.
We have original recorded sources of our religion in the original language (This is a very unique part of Islam, not available in any other ancient religions):

 A) The Quran

 B) Teachings of Muhammad (pbuh). (Or what we called "hadith")                       

Number 5 is a big point.

Six- If something doesn’t make sense to you or doesn’t seem to be right, so probably it isn't.

You need to trust your inside feelings based on what you learned in Quran and from the teaching of prophet Muhammad peace be upon him, at least to extent that you know Allah will not misguide you
Now the prophet Muhammad told us inside every one a Mufti and the Mufti consider to be your conscious telling you what is right from wrong

Seven-This is the last point, turn back to Allah for every thing you do.

You need to thank him for every good come to you, you have to turn to him for guidance and problems coming to, you have to turn to him and repent from the mistakes and be sure to turn to him in different time and be sure that he is the only one who can change anything or make anything easy for you .

I will keep referring you to point # 2