The discworld mud has five stats which represent your different phisical and mental attributes. They affect your bonus in the relevent skills. For example, magic skills are mostly dependent on the Intelligence stat, whearas faith skills are mostly dependent on the Wisdom stat.
The stats are:
As a thief, most of your primaries (skills) will be based on your Dexterity. This is because they will be covert skills, so this will mean that you will need a high dexterity.
The highest you can set a stat to is 23. I do not recomend having any stats of 23 as it is just too limiting. You are going to need other stats at a resonable level so that you can be good at other things and you have a limited amount of points to spend. See the help file "help rearrange" for more info on this. It is especially true for thieves which have fighting skills as a primary as these skills are based mostly on Strength. Also, a low Constitution will mean you will have trouble getting a lot of hit points. Keep in mind though, that having a stat of 23 means you are very good at some things.
So whatever you choose your stats to be, choose wisely. It is forever. It is also a matter of personal choice, I cannot say "this is what your stats should be." so don't ask me to. But here is advice:
I don't recommend having a con of above 12.
This is just my opinion! Ask ten different experienced thieves and you will get ten different and conflicting pieces of advice, chances are that many will disagree with the above advice.
You will certainly regret having a dex of less then 20. Too little strength will frustrate you as you will not be able to carry your loot or armour easily.
To finish, here is my rearrange. Keep in mind I am a Mugger. This is probably not a typical mugger refresh though, I like being sneaky, but having fighting is definitely good. I spent much of my time as a Prowler, so I am heavily into having a very high dexterity. Also, I have done a quest which gives me an extra point of con, which is why I have one more stat point then is in the pool.
St: 15; Dex: 22; Co:13; Wis: 8; Int:8;
Enjoy
By the way, I lied, it is possible to change your stats via a big bloke with a hammer in OC. However, this costs money and you can only move one stat point at a time. Also, you can not use him very often. Rumours on this point every which way, but I have never heard of anyone using him more then once every real time three months. In other words, get it right first time. I am currently working on moving con into st.