If your product is not strong as competition how you attract first time buyer to buy your product again?

Develop the product, else spend on advertising.

sometimes by giving the buyer special prices give free warranty and some promoting for the product

attractive prices and product awareness and best selling skills too

There is competition every where and still people are selling and how is this happening? A big question to ponder! NEED based selling generally does not get into the WAR of strengths and weaknesses of products available in the market.
When some smart sales person sells a particular feature of the product it becomes his/her product strength.
If the same feature is not available in another product of another sales person then its seen as the products weakness.
It means that the earlier sales person converted that particular feature of the product into NEED of the buyer and the buyer was sold on the same.
Therefore do the same for your product with its features and convert that into buyers NEED and you will enjoy selling.
Happy selling!

I believe it be more to concentrate on astectic point and a sleek development of product.

Well, I hope the product is in in good shape.
In that case,1.
Having experienced ppl in your sales team might be of an advantage.
Its really tough to convince a customer ( aggressive ) to have even one of your products on their space.
The space for which they will have to pay for.
But if you have ppl with good skills, it should be possible.2.
Once you have your product at a customer place ( high valued customer ) and if they are willing to try it out, if you have a combination of a good support engineering team and ppl who can extract honest first had experience of the customer ( sales team who are allowed t interact with the supplier more effectively ? ), you will get really good feedbacks with which you improve the product until you are appreciated in that segment of the market.3.
Develop products faster -> get feedbacks faster from ppl who matters ->improve it further -> have it installed at the expense of the best customer and get them to use it before our competitors -> have exceptionally gr8 support engineers at customer base especially for a new product to extract effective feedbacks faster.
very close co-ordination b/w the R&D engineers and the support engineers once the prototype is launched at the customer base .

First of all to make s.w.a.t analysis for the market, to know what are the strength and weakness points of our product.
Then, make a reasonable pricing to be competitor comparing to the others.
Then the marketing stating from a promotion concerning Price discount, warranty contract and/or free samples or test for the product and make a survey.
Also, Mass-media has a great effect.

the question is vague a little bit.
what type of products are you offering ? why not to improve your product so you can target a niche market where you can be a solo player ( big fish strategy ) , improve your product so you can compete.
if your product is has lower quality from you competitors and your price is similar, you will face a complete failure.
first you have to know who is your customer behavior ,, then you have to improve your product , its useless to come up with an existing product but with lower quality , why people should buy it ! unless you have a great added value for them ( i.e lower price , after sales services ,....) if you cannot improve your product you have to compete using one of the following as a market penetration strategies : Price increased promotion and marketing wide distribution channels

1. Promote the product showing off the maximum good points about the product through advertisements, sales executives, leaflets or notices.

2. Providing offers like buy3 get1 or selling another product for free alongwith your product or vice versa.

3. Reducing the price of the product in comparision with rival product. By doing this the profit margin gets decreased. It should be done by market analysis.

4. Selling the product by following along with top brands in the market like for electronic product we have sony, panasonic etc and for food products we have maggi, nestle.

5. Reducing the unneccessary additional costs such as transportation, machining involved in the production.   

Put the product in a good shape and several forms, ponus may be attractive and no doubt regular visits will support all these steps.

Advertise, promote the product or allocate incentives for buyer.