Does your company have a pension scheme? If so, you should join it, especially as many companies will also contribute towards it. And if you belong to a company pension scheme and you can afford it, you can make additional voluntary contributions to top it up.
If you don't belong to a company scheme you can set up a stakeholder or private pension with one of the big companies like Standard Life but you should seek advice from an Independent Financial Advisor before making a decision because some schemes have expensive set up fees. Alternatively you can make the most of your annual ISA allowance which is �7,000 a year, either putting �3000 into a Cash ISA and �4000 into equities (unit trusts) and having all the dividends reinvested or putting the full �7000 into an equity ISA which will have time to build up (although there is always a risk of a stock market downturn just as you are retiring). But pension schemes also invest in the stockmarket too, so there is always a calculated risk. The benefits of ISA's is that any income you eventually take from them will be tax free whereas any pension income will be taxed.