What is the best way of cost reduction to meet the market competition level in a predictable and particular season?

Cost reduction has to be a dynamic continuouse process.
First, you have to monitor the record of the cost items in order to maintain a realistic average level for each cost item.
Then, you have to indicate which are the most critical items which are affecting the cost structure.
Those items are the ones which worth to be attacked.
Also, another study shall be made to know what is the maximum possible level of cost reduction without affecting the final revenues.
On other words, cost reduction shall be made to the items which will not hit the target revenue.
After all the above, if the results are still not satisfactory, then the business model will be in need of a different review from other prespective.

Optimize supply chain, automate processes, and focus on high-margin products. Use data to forecast demand and adjust inventory accordingly.

Dear Mr.
Ahmed,   Yes, absolutely right, cost reduction is a dynamic and continuance process.
  But in some critical temporary situation the company will face a hard competition attack ,raised usually when the demand start slowing down or even when start moving up or for any other temporary situation , means that any reduction going to be used will be used temporary ,and can be re adjust to the normal level after the storm passed , is it the manpower (the assets and loyalty ),general expenses(the quality of work ) ,production (the quality of products)or vendor ( the profit's back bone ).witch one we can ask for their temporary help.
  From my point of view, I will never go for production cost revision because it supposed to be in the level of product's strategic quality..it is untouchable .
Manpower will not reflect that much power to the cost unless you made a big reduction, beside bad side effects of this action will harm the work environment and effectiveness by touching the employment security level.
Definitely, for temporary action, I will hit the general expenses to the maximum level without fear, all members should deal with that and accepte.
I will foreword the pressure to the vendors, since I m a (regular costumer for some vendors or have a strategic business agreements with other) this is the time to benefit from this relation.
Finally in some cases we can accept some loses from the end prices, but never accept a loses of the market share, 

Hi, If you are talking about a business which running for some time and is affected certain times a year due to reasons which are peculiar to the industry as a whole and will definetely happen due to seasonal nature of the business,we can certainly do a number of things because of the predictable nature of the problem.
1) Make revenue and sales projections taking into account the lean or robust seasons.
2) Plan your raw materials accordingly.
3) Manpower should be kept flexible.
Advisable to have both types of employees-On payroll & contractual.
4) Plannig the inventory to avoid overstocking as well as understocking.This can be done by analysing the sales pattern.
5) Robust season should be capitalised by having people earning by way of comissions on sale than having a large salesforce on payroll.
6) Capital expenses should be avoided during lean season.Expenses on inputs should complement a robust season.
7) Trim the 'fat'.
Never let the organisation out of proportion by swelling the employee force.Can outsource functions as per season requirement.
8) In this increased era of consumer thriftness,it is better to cut down on 'Heavy' expenses and think what benefits and perks are justified.
The first priority should always be the consumer.
When the situation is predictable and seasonal,as in your question,there are a lot of ways to cut costs.It depends on the type of industry you are in,what has been your experience facing these situations and what have you learned from them.
It gets tricky when the situation gets unpredictable.
Then it is your vision and cost cutting orientation,which defines the ultimate outcome,which as you have mentioned is a continuous and a dynamic long term process.