what kind of concepts must be taken up for mini projects by students,especially for their first project...??please reply...

Firstly, please share whether you are interested in learning things or do some project that would satisfy your faculty [ for your grades ].

If I were you I would have done

For grades
Go for any record maintenance system [ use file handling or DB ]

For learning
Don't for any record maintenance system. Try socket programming for simple chat program or implement the Linked list / Binary tree concepts.

Im doing for learning pupose..Im good at data structures like linked list,queques,stacks,array,binary trees...So nw what should be my next step...??please help

1) Try a simple calculator ( u said u were a beginner and I did it in C# )
A calculator that reads expression and returns an answer

2 + 5 - ( 4 / 2 ) should give 5

Queues, postfix can be used in this context.

2) Create a structure with a name and mobile no
Use file to store a list of names with their mobile no.
In your prog read files and load the names in a structure array ( in the form of binary tree )
Make functions to
1) Add an entry to the binary table
2) Delete an entry
3) Search an entry (most important function)

You can use the concept of LinkedList and BinaryTree (collection of lists).

Save the directory info to the file when your program exits.

File handling can be done later. Do concentrate on the three functions.

I hope my explanation of the ideas would be clear. Reply if you need any clarification

Again, these are my ideas. You can still do something else using data structures.

And how to improve programming skills...??Is that can be done by trying to write codes for tylore series etc...??or any other ways..??

Programming skill is composed of
10% knowledge on programming language
90% logical skills ( how to solve a problem )

So, try to solve as many problems (even the two that I gave in my previous post can also be considered as problems) using the programming language you are learning now.
Use different techniques to solve the problems. Learn new techniques. Implement them in your code.

P.S. I don know what tylore series is.....

your explanation is perfectly clear,thank you..I'll reply if any clarificatins are needed..I'll work on the informations that you have provided,first..Thanks again...