How to speed up Magento?

Please follow the below step:
1. Enable cache
   Just navigate to System > Cache Management and enable all cache types.
2. Re-index data
Regularly indexing Magento data will also have some impact on performance.
Under System > Index Management select all indexes and hit the “Reindex Data” submit button.
3. Enable JavaScript file merging
Combining all JavaScript files into one will greatly reduce the number of HTTP requests your Magento site makes to the server and will have a nice impact on speed.
Navigate to System > Configuration > Developer > JavaScript Settings and select “Yes” under “Merge JavaScript Files”
4. Combine CSS files
Like with JavaScript files, combining all CSS files into one will reduce load time and increase speed.
Go to System > Configuration > Developer > CSS settings and select “Yes” for “Merge CSS Files”.
5.Turn off the logs
On a production Magento installation make sure all logs are turned off!
The settings are under System > Configuration > Developer > Log Settings.
6. Run the compilation
Magento’s compilation is a great tool to speed up a production installation.
Go to System > Tools > Compilation and hit “Run Compilation Process”.
7. Enable Flat Catalog
Magento uses the EAV model to store customer and product data. This enables these objects to be incredibly extensible, but results in longer SQL queries and more reads. Enabling the Flat Catalog for Categories and Products merges product data into one table, thereby improving performance. Generally, all stores should enable Flat Catalog for Categories. Stores with over 1000 products should enable Flat Catalog for Products.
   i).In the Magento Admin, go to System > Configuration > Catalog.
   ii). Under “Frontend”, change “Use Flat Catalog Category” to YES.
   iii).Under “Frontend”, change “Use Flat Catalog Product” to YES. (optional)
   iv).Clear the cache.
   v) After complete this process must “Reindex Data”(Number 2 process).
 
The default .htaccess file that comes with Magento has several sections dealing with performance. These configurations are commented out and will need to be turned on to realize their benefit.
8. Enable Output Compression
This section will turn on the apache mod_deflate module, which compresses text, css, and javascript before it is sent to the browser. This results in a smaller download size. To enable, simply uncomment the appropriate lines so that it looks like the following:
<IfModule mod_deflate.c>
############################################
## enable apache served files compression
    # Insert filter on all content
    SetOutputFilter DEFLATE
    # Insert filter on selected content types only
    AddOutputFilterByType DEFLATE text/html text/plain text/xml text/css text/javascript
    # Netscape 4.x has some problems…
    BrowserMatch ^Mozilla/4 gzip-only-text/html
    # Netscape 4.06-4.08 have some more problems
    BrowserMatch ^Mozilla/4\.0[678] no-gzip
    # MSIE masquerades as Netscape, but it is fine
    BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
    # Don’t compress images
    SetEnvIfNoCase Request_URI \.(?:gif|jpe?g|png)$ no-gzip dont-vary
    # Make sure proxies don’t deliver the wrong content
    Header append Vary User-Agent env=!dont-vary
</IfModule>
Hope it will help you.