Unless you have the kind of budget to physically build a soundproof booth inside your home, you will need to exercise some creativity in achieving the right room acoustics for recording. Set up your recording area near a corner to achieve natural reverberation. For an inexpensive and non-invasive soundproofing solution, purchase acoustic panels that use hooks or clips for simple installation and removal.
Although you can purchase adapters that allow you to connect all of your instruments and microphones directly to your PC (one or two at a time), a USB mixer will allow you to connect all of your inputs simultaneously, feed the audio signals directly to your PC and adjust your EQ frequencies and other parameters in real time.
Most digital audio programs contain numerous effects that you can apply to any digital recording. Many inputs, though, require some effects processing during the initial recording phase in order to achieve optimal sound quality. For example, by applying multiband compression to your guitars during the recording phase, you can achieve a clean guitar sound from the very beginning, rather than repairing the sound later. Connect your effects processor to your mixing board using the "Aux-Send" (for output) and "Aux-Return" (for input) jacks.
Each output will give you a different perspective on a recording, so use at least three outputs for playback. For example, you should use monitor headphones and monitor speakers as your essential high quality output sources, and you might also use a low quality output source like your computer speakers as well. Your mix may sound great through your headphones, but terrible through your speakers. These variations can clue you in as to which aspects of your mix require improvement.
Although many audio recording programs exist, you will need a professional production program for precise recording, mixing and post production. Look for programs that support multi-tracking (the ability to record your music in layers, as you would in a professional studio), MIDI sequencing (the reading and manipulation of digital music notes), track automation (the ability to edit each effect and parameter of your recordings in real time), digital mixing, EQ and effects options. If you only wish to record as a hobby, you can use simpler software.
By including a MIDI controller (any MIDI keyboard or controller keyboard) in your setup, you can use virtual instruments to create additional layers of music whenever a recording lacks something essential. If, for example, you have a recording with guitar and drums but no bass, you can select a bass sound using your audio software and play the bass notes using your MIDI controller. You can also create entire electronic compositions using just your controller and your software.